METHOD AND APPARATUS FOR OBTAINING BLOOD FOR DIAGNOSTIC TESTS

Abstract: Method and apparatus for obtaining a sample of blood from a patient for subsequent diagnostic tests, e.g., glucose monitoring. In one aspect of the invention, the method comprises the steps of: (a) forming an unobstructed opening in the area of the skin from which the sample of blood is to be extracted; and (b) extracting the sample of blood from the unobstructed opening in the skin, with the aid of a vacuum and a stretching of the skin. In another aspect of the invention, an apparatus for carrying out the method described previously is provided. The apparatus comprises: (a) a device for forming an unobstructed opening in an area of skin from which said sample is to be extracted, preferably a lancing assembly; and (b) a vacuum pump. Preferably, the apparatus also includes a housing. In a further aspect of the invention, a pneumatic lancing assembly is provided. The pneumatic lancing assembly uses differential gas pressure to thrust a lancet into skin tissue. In another aspect of this invention, an article is provided for an article capable of both collecting blood and detecting an analyte in that blood. The article, which contains an appropriate detection element for determining the amount of analyte in the blood, can be used in conjunction with a meter that measures the signal generated by the detection element of the article.

Description: METHOD AND APPARATUS FOR OBTAINING BLOOD FOR DIAGNOSTIC TESTS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method and apparatus for obtaining samples of blood for diagnostic purposes. 2. Discussion of the Art The prevalence of diabetes has been increasing markedly in the world. At this time, diagnosed diabetics represent about 3% of the population of the United States. It is believed that the total actual number of diabetics in the United States is over 16,000,000. Diabetes can lead to numerous complications, such as, for example, retinopathy, nephropathy, and neuropathy. The most important factor for reducing diabetes-associated complications is the maintenance of an appropriate level of glucose in the blood stream. The maintenance of the appropriate level of glucose in the blood stream may prevent and even reverse many of the effects of diabetes. Glucose monitoring devices of the prior art have operated on the principle of taking blood from an individual by a variety of methods, such as by needle or lancet. An individual then coats a paper strip carrying chemistry with the blood, and finally inserts the blood-coated strip into a blood glucose meter for measurement of glucose concentration by determination of change in reflectance. The medical apparatus of the prior art for monitoring the level of glucose in the blood stream required that an individual have separately available a needle or lancet for extracting blood from the individual, strips carrying blood chemistry for creating a chemical reaction with respect to the glucose in the blood stream and changing color, and a blood glucose meter for reading the change in color indicating the level of glucose in the blood stream. The level of blood glucose, when measured by a glucose meter, is read from a strip carrying the blood chemistry through the well-known process of reading reflectometers for glucose oxidation. Generally lancets comprise a blade and a pressable end opposed thereto, with the blade having an acute end capable of being thrust into skin of a human. By striking the pressable portion, the acute end of the blade will pierce the skin, for example, of the finger. The finger lancet is primarily used to obtain small volumes of blood, i. e., less than 1 mL. Diabetics use the finger lancet to obtain volumes of blood less than 25 μL for analysis for glucose. A small amount of blood for the blood test will ooze out of the skin. There are many small blood vessels in each finger so that a finger can be squeezed to cause a larger drop of blood to ooze. The finger is one of the most sensitive parts of the body; accordingly, the finger lancet leads to even more pain than what would be experienced by extracting blood via lancet at a different body site. The finger lancet presents another problem because of the limited area available on the fingers for lancing. Because it is recommended that diabetics monitor their blood glucose levels four to six times per day, the limited area on the fingers calls for repeated lancing of areas that are already sore. Because fingers are sensitive to pain, it is a recent tendency that the arm is subjected to blood sampling. See, for example, U. S. Patent No. 4,653,513. The device of U. S. Patent No. 4,653,513 comprises a cylindrical housing and a lancet support, which has a gasket or flexible portion slidably accommodated in the housing. Springs will retract the lancet support to thereby reduce air pressure in the housing so that it sucks a blood sample, automatically and immediately after a lancet pierces the skin. See also U. S. Patent No. 5,320,607, which discloses a device comprising a sealed vacuum chamber in a state of preexisting reduced pressure, a support member for the sealed vacuum chamber, the support member defining a suction portion adjacent the sealed vacuum chamber, the suction portion, in cooperation with the sealed vacuum chamber, exposing an area of the skin of a patient to a reduced pressure state when the device is actuated, and means arranged within the suction portion for slightly rupturing a portion of the area of skin of the patient exposed to the reduced pressure state. Because the blood volume requirements for a standard glucose test strip are typically 3 μL or more, an area of the body that can generate that much blood from a lancet wound must be used. It is believed, however, that improvements in glucose test strip technology will reduce the volume of blood needed to 1 to 3 μL. Because the finger is well supplied with blood and the amount of blood can be increased by squeezing the finger after lancing, the finger is the currently preferred body site for lancing, even though lancing of the finger is painful. A less painful technique for obtaining body fluids could be found if a reliable method were found for lancing a body part that is less sensitive to pain than the finger and obtaining a useful amount of blood from that body part. A body part such as the forearm is much less sensitive to pain than the finger, but the amount of blood resulting from the lancing procedure is generally of an inadequate volume for use with current detection technology. Ways of increasing blood flow to the finger are common knowledge. The recommendation is made to diabetics to run their finger under hot water prior to lancing to improve the blood flow in the finger and the amount of blood collected from the finger. Running hot water over a body part to improve blood flow is impractical for areas such as the forearm or thigh. The availability of hot water is also a concern. The blood obtained from a lancet stick has typically been manually transferred by the user from the finger to the detector. However, such manual transfer is difficult for users who exhibit poor dexterity, poor eyesight, or who are prone to shaking (hypoglycemic diabetics). Manual transfer can also lead to errors in the glucose determination if too much or too little blood is transferred. It would therefore be desirable to develop a technique and apparatus for obtaining blood for diagnostic purposes in a painless, reliable manner. Conventional lancing devices, such as those described in U. S. Patent Nos. Re. 32,922, 4,203,446, 4,990,154, and 5,487,748, accept commercially available, disposable lancets. Most conventional lancing devices are not integrated with a diagnostic instrument. A conventional lancing mechanism typically consists of a housing, a guided shaft having a lancet holder at one end, a main spring (usually helical) that supplies the mechanical energy to axially accelerate the shaft, and a return spring that partially retracts the shaft after lancing has occurred. The user must first insert a lancet into the holder, then manually slide the shaft until the main spring is compressed and the shaft is locked into its "cocked" position, then place the device against the skin, then press a trigger, which releases the shaft, thereby driving the lancet into the skin. The lancet is quickly retracted from the skin by the force of the return spring. Conventional lancing devices would have several disadvantages for an apparatus that combines the processes of lancing, fluid collecting, and analyte sensing into one automated instrument. The first disadvantage is the necessity of manually cocking the lancing mechanism prior to each use. Manual cocking is inconvenient for the user and generally adversely affects the automated characteristics of an integrated instrument. Manual cocking also prohibits rapid, sequential lancing of the target skin. Sequential lancing could increase the volume of biological fluid collected. The second disadvantage is that the mechanical trigger can be accidentally pressed by the user if the device is mishandled. Accidental triggering of the lancet could injure the user and cause technical problems within an automated lancing system. The user would be further inconvenienced by having to re-cock the mechanism after accidental triggering. The third disadvantage is that the conventional return spring is generally not able to completely retract the lancet, due to the opposing force of the main spring. Partial retraction may subject the user to accidental punctures when handling the instrument before or after use, particularly when the lancet is located near other disposable components, such as fluid sample collection strips. It would therefore be desirable to provide a lancing device that eliminates one or more of the foregoing disadvantages. SUMMARY OF THE INVENTION This invention provides a method and apparatus for extracting a sample of blood from a patient for subsequent diagnostic tests, e.g., glucose monitoring. In one aspect of the invention, the method comprises the steps of: (a) forming an unobstructed opening in the area of the skin from which the sample of blood is to be extracted; and (b) extracting the sample of blood from the unobstructed opening in the skin, with the aid of vacuum and stretching of the skin. In a preferred embodiment of the method, step (a) is preceded by the step of increasing the availability of blood in the portion of the skin from which the sample is to be extracted. In this preferred embodiment, the availability of blood in the portion of the skin from which the sample is to be extracted can be increased by means of a vacuum, which is applied to the surface of the skin in the vicinity of the opening prior to forming the opening in the skin. The vacuum causes the portion of the skin in the vicinity of the blood extraction site to become engorged with blood. The vacuum also causes the portion of the skin in the vicinity of the blood extraction site to become stretched. An opening in this stretched portion of skin can be formed with a cutting or puncturing device, e.g., a lancet, or other device capable of forming an opening in the skin, e. g., a laser or a fluid jet. If a cutting or puncturing device is used to form the opening, it must be retracted from the opening prior to the step of extracting the sample of blood from the opening. This retraction will allow the unrestricted flow of blood through the opening. After the opening is formed, a vacuum is used to aid in extracting the sample of blood from the opening in the skin. The sample can be analyzed from the drops of blood that collect on the surface of the skin at the site of the opening by applying the blood directly to a glucose detector. It is preferred, however, that the sample be collected in such a manner, e. g., via a capillary tube, that it can be analyzed by conventional diagnostic devices, such as, for example, a biosensor. In another preferred embodiment, the sample can be collected in a collection zone that is integrated with a conventional diagnostic device, e. g., a biosensor. If a glucose detector is used, it may be held stationary within the device throughout the blood collection procedure or may be moved nearer the lancing site after the lancet is retracted by a triggering or other mechanism. In an alternative of the aforementioned preferred embodiment, the availability of blood in the area of the skin from which the sample is to be extracted can be increased by means of applying thermal energy to that area of skin. The thermal energy causes the blood in that area of the skin to flow more rapidly, thereby allowing more blood to be collected per given unit of time. In this alternative embodiment, steps (a) and (b) can be carried out in the same manner as they were carried out in the aforementioned preferred embodiment. In another aspect of the invention, an apparatus for collecting a sample of body fluid for analysis in a diagnostic test, e. g., blood, is provided. In a preferred embodiment, the apparatus comprises: (a) a housing; (b) a device for forming an unobstructed opening in an area of skin from which said sample is to be extracted, preferably a lancing assembly; and (c) a vacuum pump. It is also possible to dispense with the housing. However, the housing is preferred for the convenience of the patient and the protection of the components. The vacuum pump requires a source of power. If the apparatus includes a housing, the source of power can be disposed within the housing. Alternatively, the source of power can be external to the housing. The preferred device for forming an unobstructed opening in the area of the skin from which the sample of blood is to be extracted is a lancing assembly, which comprises a lancet for forming an opening in the skin. Alternatively, the unobstructed opening in the skin can be formed by a laser or a fluid jet. The vacuum pump can serve the dual purposes of (1) stretching the skin and (2) enhancing the extraction of the sample of blood from the unobstructed opening in the skin. Preferably, the vacuum pump can serve the triple purposes of (1) stretching the skin, (2) increasing the availability of blood to the area of the skin from which the sample is to be extracted, and (3) enhancing the extraction of the sample of blood from the unobstructed opening in the skin. Preferably, the housing further contains electronics having programmed instructions to switch the vacuum pump on and off to maintain the desired level of vacuum. The apparatus preferably contains valves, such as, for example, solenoid valves, for triggering the lancet of the lancing assembly and releasing the vacuum at the conclusion of the blood extraction procedure. The apparatus can optionally contain a heating element to increase the availability of blood to the area of the skin from which the sample is to be extracted. The apparatus can also contain a glucose detector integrated with the apparatus, e. g., a biosensor, to analyze the sample of blood collected by the apparatus. In another aspect of this invention, a lancing assembly that uses differential gas pressure to thrust a lancet into skin tissue has been developed. This lancing assembly effectively utilizes low-pressure gas, which is preferably provided by the aforementioned vacuum pump, and high-pressure gas, which is preferably provided by ambient air surrounding the apparatus, to thrust the lancet, puncture the skin, and then retract the lancet from the skin to produce an unobstructed opening to allow access to biological fluid. The lancing assembly eliminates the need to manually force the lancing mechanism into a latched, or "cocked", position prior to each use, and also eliminates the need for a mechanical trigger to release the latch to allow the lancet to be thrust into the skin. Elimination of the requirement to manually cock the lancing mechanism allows the lancing assembly to be controlled exclusively by electronic means. Such means of control is desirable when used in conjunction with an automated instrument, or when a continuous series of lancing steps is desired. The lancing assembly that utilizes differential gas pressure comprises: (a) a holder for holding a lancet assembly; (b) a means for providing sufficient force to cause the holder to be maintained in a position whereby a lancet assembly in the holder would be positioned away from the skin of the patient; and (c) a means for allowing a gas to provide sufficient force to overcome the force provided by the holder maintaining means, whereby the gas causes the holder to be moved to a position whereby a lancet in the holder would be able to pierce the skin of the patient. In one embodiment, the lancing assembly comprises a housing, a lancet holder, a piston for moving the lancet holder, a bore in which the piston moves toward and away from the target skin tissue, a means for biasing the piston, e. g., a return spring or a bellows, away from the target skin tissue, and a cap. The housing has a manifold into which a three-way valve can be fitted. The three- way valve selectively allows high-pressure air from a source external to the housing to pass through an inlet port to a bore port, thereby causing the level of pressure in the bore to increase. The air pressure in the bore thrusts the piston toward the target skin tissue while simultaneously compressing the piston biasing means. The piston is halted by the cap or by a structure in the instrument designed to limit the penetration depth of the lancet in the skin. The three-way valve then directs the air in the bore to flow out through an exit port to a source of low-pressure air, e. g., an evacuated air cavity in the apparatus, thereby causing the level of pressure in the bore to decrease, and consequently allowing the piston biasing means to force the piston back to its pre-thrust position in the bore. In another aspect, this invention provides an article capable of both collecting blood and detecting an analyte in that blood. Preferably, the article is also capable of measuring the amount of analyte in the blood. The article, which contains an appropriate detection element for determining the amount of analyte in the blood, can be used in conjunction with a meter that measures the signal generated by the detection element of the article. In one embodiment, the article is a multiple-layer element comprising: (a) a layer capable of receiving blood and transporting the blood received by means of chemically aided wicking; (b) a layer capable of detecting the presence of analyte or measuring the amount of analyte in blood; and (c) a layer that can be placed in contact with a meter, the meter- contactable layer overlying the blood-transporting layer, said layer (a) capable of transporting blood to said layer (b). In a preferred embodiment, the article is a multiple-layer element comprising: (a) a covering layer having an opening therein; (b) a layer, overlying the covering layer, capable of receiving blood through the opening in the covering layer and transporting blood by means of chemically aided wicking; (c) a layer that can be placed in contact with a meter, the meter- contactable layer overlying the blood-transporting layer; and (d) a layer capable of detecting the presence of analyte or measuring the amount of analyte in blood, which layer is disposed between the covering layer and the meter-contactable layer and is capable of receiving blood from the blood-transporting layer. An optional overcoat layer can be interposed between the covering layer and the meter-contactable layer to restrict the flow of blood in the blood-transporting layer. In another embodiment, the blood-transporting layer can be eliminated. In this embodiment, the meter-contactable layer and the covering layer utilize capillary action to tranport the blood by capillary flow to the detecting layer. In order to use the multiple-layer element, a vacuum is used to stretch the skin and draw the skin into contact with the covering layer of the element. The vacuum is applied for a sufficient period of time to cause blood to pool in the stretched skin. Then an unobstructed opening is formed in the skin, typically by a retractable lancet. Blood emerges from the unobstructed opening in the skin and enters the blood-transporting layer. The opening in the covering layer renders it possible for the blood emerging from the unobstructed opening in the skin to enter the blood-transporting layer. The blood then moves along or through the blood- transporting layer to the detecting layer. Preferably, the detecting layer comprises an electrochemical sensor or an optical sensor. A chemical reaction occurs at the surface of the detecting layer. The result of the chemical reaction can then be read by a meter. The multiple-layer element integrates the the blood-transporting layer, the meter-contactable layer, the detecting layer, and, when employed, the covering layer into one element. This integrated element can be made at a low enough cost to be disposable. The multiple-layer element makes it possible to obtain accurate results with small samples of blood, because no blood is spilled during transfer of the blood to the detecting layer. The multiple-layer element can wick up blood that emerges from the unobstructed opening formed in the skin and direct the blood to the detecting layer of the multiple-layer element where a diagnostic test, such as, for example, measurement of concentration of analyte, e. g., glucose, in blood, is made. Transfer of the blood by manual means is not required. The detecting layer can also be used for the additional purpose of sending a signal to the blood collecting apparatus of this invention to release the vacuum when sufficient blood has been drawn into the multiple-layer element to provide a reliable diagnostic test. The multiple-layer element can also be used as a barrier to stop a lancet assembly to control the depth of the unobstructed opening formed in the skin. The method and apparatus of this invention provide several advantages over the methods and apparatus of the prior art. First, a sufficient amount of blood can be extracted from parts of the body, other than the finger, for conducting glucose monitoring tests. Second, by rendering other parts of the body suitable for extracting blood, the use of a painful finger lance can be avoided. Third, by increasing the availability of blood at the site where the blood is to be extracted, the period of time required for extracting the sample can be reduced. Because of these advantages, the diabetic patient is more likely to monitor glucose levels in the blood at the intervals prescribed by his doctor. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the components of a preferred embodiment of the apparatus of this invention. In this Figure, the cover of the housing is removed. FIG. 2 is a schematic diagram illustrating how a vacuum causes a portion of the skin to become stretched prior to the formation of an opening in the skin from which the sample of blood is extracted. FIG. 2 also illustrates the spatial relationship between the nosepiece of lancing assembly and a glucose detector, e.g., a biosensor. FIG. 3 is a block diagram illustrating the electronics of the preferred embodiment. FIG. 4 is a schematic diagram illustrating an alternative seal for the vacuum of the device of the present invention. FIG. 5 is a perspective view of an embodiment of the apparatus of this invention. In this figure, the housing of the apparatus is open. FIG. 6 is a perspective view of an embodiment of the apparatus of this invention. In this figure, the housing of the apparatus is open. FIG. 7 is a perspective view of an embodiment of the apparatus of this invention. In this figure, the housing of the apparatus is open. FIG. 8 is a perspective view of an embodiment of the apparatus of this invention. In this figure, the housing of the apparatus is open. FIG. 9 is a perspective view of an embodiment of the apparatus of this invention. In this figure, the housing of the apparatus is open. FIG. 10 is a perspective view of an embodiment of the apparatus of this invention. In this figure, the housing of the apparatus is open. FIG. 11 is an elevational view, in cross section, of one embodiment of the lancing assembly of this invention in assembled configuration. FIG. 12 is an exploded view, in cross section, of the lancing assembly of FIG. 11 . FIG. 13 is a schematic diagram illustrating the positioning of the components of the lancing assembly of this invention. In this figure, the lancet assembly has not yet been inserted into the lancet holder and the valve has not yet been inserted into the valve manifold. FIG. 14 is a schematic diagram illustrating the positioning of the components of the lancing assembly of this invention. In this figure, the lancet has been inserted into the lancet holder and the valve has been inserted into the valve manifold. FIGS. 15A, 15B, and 15C are schematic diagrams illustrating the lancing assembly of this invention in the pre-lancing position, the lancing position, and the post-lancing position, respectively. FIG. 16 is an elevational view, in cross section, of another embodiment of the lancing assembly of this invention in assembled configuration. FIG. 17 is an exploded view, in cross section, of the lancing assembly of FIG. 16. FIG. 18 is an elevational view, in cross section, of another embodiment of the lancing assembly of this invention in assembled configuration. FIG. 19 is an exploded view, in cross section, of the lancing assembly of FIG. 18. FIG. 20 is an elevational view, in cross section, of the lancing assembly of this invention installed in an embodiment of an apparatus of this invention. FIGS. 21 A and 21 B are exploded perspective views of a multiple-layer element for collecting blood and detecting an analyte. FIG. 21 B is a peeled-apart exploded perspective view. FIG. 22 is a top plan view of one embodiment of a multiple-layer element wherein the blood-transporting layer is a fine mesh. FIG. 23 is a bottom plan view of the embodiment of the multiple-layer element of FIG. 22. FIG. 24 is a top plan view of one embodiment of a multiple-layer element wherein the blood-transporting layer is a coarse mesh. FIG. 25 is a top plan view of one embodiment of a multiple-layer element wherein the blood-transporting layer is a fine mesh having an opening formed therein. FIG. 26A is a top plan view of one embodiment of a multiple-layer element wherein the blood-transporting layer is a fine mesh. The meter-contactable layer has two openings punched therein. FIG. 26B is a top plan view of one embodiment of a multiple-layer element wherein the blood-transporting layer is a fine mesh. The meter-contactable layer has a single opening therein. FIG. 27 is a top plan view of one embodiment of a multiple-layer element wherein the blood-transporting layer abuts one end of the element. FIG. 28 is an exploded elevational view of a multiple-layer element of this invention. FIGS. 29A, 29B, 29C, and 29D schematically illustrate a procedure by which the method of this invention is carried out with the multiple-layer element of this invention. FIG. 30 is a graph illustrating average electrical charge as a function of glucose level in the blood. FIG. 31 is a graph illustrating pain of lancet of forearm compared to pain of lancet of finger. FIG. 32 is an elevational view of a cross section of a preferred embodiment of a nosepiece of this invention. FIG. 33 is a series of elevational views of cross sections of various embodiments of nosepieces suitable for use in this invention. FIGS. 34A, 34B, 34C, and 34D are schematic diagrams of the positioning of the nosepiece of the apparatus of this invention relative to the lancing assembly, the detection element, and the skin prior to application of vacuum, during application of vacuum, during lancing, and during blood collection and analysis, respectively. FIG. 35 is a series of elevational views of cross sections of various embodiments of nosepieces suitable for use in this invention. FIG. 36 is a graph illustrating the effect that various embodiments of nosepieces have on filling time of a detecting element. FIG. 37 is a graph illustrating the average time to fill a multiple-layer element as a function of the nosepiece used. FIG. 38 is a graph illustrating the percent filled, as a function of the nosepiece used. FIG. 39 is a series of elevational views of cross sections and top plan views of various embodiments of nosepieces suitable for use in this invention FIG. 40 is a graph illustrating airflow rate as a function of the nosepiece used. FIG. 41 is a graph illustrating the average volume of blood collected as a function of the material used to make the seal of the nosepiece assembly. FIG. 42A is an elevational view of a cross section of a preferred embodiment of a nosepiece of this invention, wherein the seal is in a first position. FIG. 42B is an elevational view of the nosepiece of FIG. 42A, wherein the seal is in a second position. FIG. 43, comprising FIGS. 43A through 43C, depicts a perspective view of an embodiment of the apparatus of this invention. In FIG. 43A and 43B, the housing of the apparatus is open. In FIG. 43C, the housing of the apparatus is closed. FIG. 44, comprising FIGS. 44A and 44B, depicts a perspective view of an embodiment of the apparatus of this invention. In FIG. 44A, the housing of the apparatus is open. In FIG. 12B, the housing of the apparatus is closed. FIG. 45, comprising FIGS. 45A through 45E, depicts a partial cross-sectional drawing of an embodiment of the apparatus of this invention. In FIG. 45A, the housing of the apparatus is open. In FIG. 45B, the housing of the apparatus is partially open. In FIG. 45C through 45E, the housing of the apparatus is closed. FIG. 46, comprising FIGS. 46A through 46C, depicts a partial cross-sectional drawing of an embodiment of the apparatus of this invention. In FIG. 46A through 46C, the housing of the apparatus is closed. FIG. 47 is a chart indicating blood collection results for an embodiment of the apparatus of this invention. FIG. 48 is a chart indicating blood collection results for an embodiment of the apparatus of this invention. FIG. 49 is a chart indicating blood collection results for an embodiment of the apparatus of this invention. DETAILED DESCRIPTION The embodiments of this invention require the following steps to carry out the function of obtaining a sample of blood for carrying out a diagnostic test, e. g., glucose monitoring: (a) a housing having a sealable chamber located therein and a sealable opening in fluid communication with said sealable chamber, (b) a power source, (c) a vacuum pump operably connected to said power source, said vacuum pump in communication with said sealable chamber, (d) a lancing assembly positioned within said sealable chamber, said lancing assembly capable of moving a lancet towards said sealable opening, and (e) a fluid collector positioned in said sealable chamber, said fluid collector in fluid communication with said sealable opening. An unobstructed opening in the area of the skin from which the sample of blood is to be extracted is formed by a piercing device or some other type of device capable of forming an unobstructed opening in the skin. Piercing devices suitable for this invention include, but are not limited to, mechanical lancing assemblies. Other types of devices capable of forming an unobstructed opening in the skin include, but are not limited to, lasers and fluid jets. Other types of devices capable of forming an unobstructed opening in the skin can be used, and this disclosure should not be construed so as to be limited to the devices listed. Mechanical lancing assemblies are well-known in the art. These assemblies comprise standard steel lancets, serrated devices, and multiple tip devices. The lancets can be made from metal or plastic. Multiple tip devices provide redundancy, which can reduce the number of failures and increase the volume of blood extracted. Lasers suitable for forming an unobstructed opening in the skin to draw blood are also well-known in the art. See for example, U. S. Patent Nos. 4,775,361 , 5,165,418, 5,374,556, International Publication Number WO 94/09713, and Lane et al. (1984) IBM Research Report - "Ultraviolet-Laser Ablation of Skin", all of which are incorporated herein by reference. Lasers that are suitable for forming an unobstructed opening in the skin include Er.YAG, Nd:YAG, and semiconductor lasers. Fluid jets suitable for forming an unobstructed opening in the skin employ a high pressure jet of fluid, preferably a saline solution, to penetrate the skin. Regardless of what type of device is utilized to form an unobstructed opening in the skin, the opening formed by the device must be unobstructed. As used herein, the term "unobstructed" means free from clogging, hampering, blocking, or closing up by an obstacle. More specifically, the expressions "unobstructed opening in the area of the skin from which the sample is to be extracted", "unobstructed opening in the skin", and the like are intended to mean that the portion of the opening below the surface of the skin is free from any foreign object that would clog, hamper, block, or close up the opening, such as, for example, a needle of any type. For example, if a lancet is used to form the opening, it must be retracted from the opening prior to the commencement of the extraction of blood. Because lasers and fluid jets do not require contact with the skin to form openings in the skin, these types of devices typically provide unobstructed openings. However, these expressions are not intended to include foreign objects at the surface of the skin or above the surface of the skin, such as, for example, a glucose monitor. This feature, i. e., the unobstructed opening, can be contrasted with the opening used in the method and apparatus described in U. S. Patent No. 5,320,607, in which the piercing and cutting means remains in the skin during the duration of the period of blood extraction. By leaving the opening unobstructed, blood can be extracted much more rapidly from the opening than it would be extracted if the piercing and cutting means were allowed to remain in the opening. In addition, the requirement of an unobstructed opening exposes the body to a foreign object either not at all or for only a very short period of time, which is welcomed by the patient. The step of extracting the sample of blood from the opening in the skin is carried out by a combination of extraction enhancing elements. Extraction enhancing elements suitable for use in this invention include, but are not limited to, vacuum, skin stretching elements, and heating elements. It has been discovered that when these elements are used in combination, the volume of blood extracted is greatly increased, particularly when a vacuum is applied in combination with skin stretching. In this combination, the vacuum not only causes the blood to be rapidly removed from the unobstructed opening by suction, it also causes a portion of the skin in the vicinity of the opening to be stretched. Stretching of the skin can be effected by other means, such as mechanical means or adhesives. Mechanical means include devices for pinching or pulling the skin; adhesives bring about stretching of the skin by means of pulling. It is preferred to use a vacuum to effect stretching of the skin. Like a vacuum, a heating element operates more effectively in combination with other techniques, e. g., stretching of the skin. This feature, i.e., the extraction enhancing element, can be contrasted with the system described in U.S. Patent No. 5,279,294 in which no such extraction enhancing elements are utilized and the system described in European Patent Applications 0351892 and 0127958, wherein the sensor is either needle-like in nature or fits within a hollow needle. In the preferred embodiment of this invention, step (a), the step of forming the unobstructed opening, is preceded by the step of increasing the availability of blood at the area of the skin from which the sample is to be extracted. The availability of blood at a given area of the skin can be increased by at least two methods. In one method, a vacuum can be used to cause blood flowing through blood vessels to pool in the area of the skin where the vacuum is applied. In another method, heat can be used to cause blood flowing through blood vessels to flow more rapidly in the area of the skin where heat is applied, thereby allowing a greater quantity of blood to be extracted from the blood extraction site per unit of time. Although the step of increasing the availability of blood in the vicinity of the blood extraction site is not required, the employment of this step can result in a greater volume of blood extracted. Elements for increasing the availability of blood at a blood extraction site that are suitable for use in this invention include, but are not limited to, vacuum, localized heating element, skin stretching element, and chemicals. As stated previously, applying a vacuum to the area of the skin from which blood is to be extracted can increase blood availability under and within the skin at the application site. The vacuum can also be used to stretch the skin upwardly into a chamber, thereby increasing pooling of blood under and within the skin. This combination of vacuum and skin stretching can be an extension of the combination used to extract blood from the opening in the skin, as previously described. It is well-known that heat can increase perfusion on the large scale of a limb or a finger. Chemical means, such as histamine, can be used to cause a physiological response to increase perfusion under and within the skin. In the preferred embodiments of the invention, the extracted blood is also collected. The step of collecting the sample of blood can be carried out in a variety of ways using a variety of fluid collectors. For example, the blood can be collected in capillary tubes or absorbent paper. Alternatively, the blood can be allowed to remain in the lancet assembly, from which it can used directly in a diagnostic test. Most preferably, the sample of blood is collected on the application zone of a glucose detector, from where it can be used directly to provide an indication of the concentration of glucose in the blood. Such a glucose detector may be held stationary within the device throughout the blood collection procedure or may be moved nearer the lancing site after the lancet is retracted by a triggering or other mechanism. The apparatus of the present invention may contain more than one fluid collector. A sensor pack containing a plurality of blood glucose sensors is disclosed in EPO 0732590A2. Regardless of the manner in which the blood sample is collected, the sample can be analyzed at a time later than the time of collection or at a location remote from the location of collection or both. A preferred embodiment of the invention will now be described in detail. Referring now to FIG. 1 , blood extraction device 10 comprises a housing 12. Disposed within the housing 12 are a vacuum pump 14, a lancing assembly 16, a battery 18, and electronics 20. A switch 22 is provided to activate electronics 20. The housing 12 is preferably made from a plastic material. It is preferably of sufficient size to contain all of the components that are required for forming an unobstructed opening in the area of the skin from which the sample of blood is to be extracted, extracting the sample of blood from the unobstructed opening in the skin, preferably with the aid of a vacuum and a stretching of the skin, and collecting the extracted sample in an amount sufficient to carry out a diagnostic test. Methods of preparing the housing 12 are well-known to one of ordinary skill in the art. As stated previously, the housing 12 is not required, but is preferred for the convenience of the patient and the protection of the components. The vacuum pump 14 must be capable of providing a vacuum that will provide sufficient suction to stretch the portion of the skin in the region from which the sample of blood is to be extracted. Typically, the portion of stretched skin is raised a distance of 1 to 10 mm, preferably 3 to 5 mm, from the plane of the body part of which it is a portion. As the suction provided by the vacuum pump 14 is stretching the appropriate portion of skin, the suction provided by the vacuum pump 14 also causes the stretched portion to become engorged with blood. The level of suction provided must be sufficient to cause a relatively large volume of blood to become engorged at the point that the vacuum is applied. The vacuum pump 14 must also be capable of providing sufficient suction to extract blood from the opening in the skin at a rate sufficient to extract at least 1 μL of blood within a period of five minutes. A vacuum pump 14 that is suitable for the device of this invention can be a diaphragm pump, a piston pump, a rotary vane pump, or any other pump that will perform the required functions set forth previously. Typically, the vacuum pump 14 employs a self-contained permanent magnet DC motor. Vacuum pumps that are suitable for this invention are well-known to those of ordinary skill in the art and are commercially available. A vacuum pump suitable for use in the present invention is available from T-Squared Manufacturing Company, Nutley, NJ, and has the part number T2-03.08.004. The vacuum pump 14 is preferably capable of providing a pressure of down to about -14.7 psig, and is more preferably operated at from about -3.0 psig to about -10.0 psig. The area of the skin subjected to vacuum preferably ranges up to about 50 cm 2 , more preferably from about 0.1 to about 5.0 cm 2 . The period of vacuum application prior to forming the opening in the skin, i. e., for increasing the availability of blood to the application site, preferably ranges up to about 5 minutes, preferably from about 1 to about 15 seconds. The period of vacuum application subsequent to forming the opening in the skin, i. e., for aiding in the extraction of blood from the unobstructed opening, preferably ranges up to about 5 minutes, preferably from about 1 to about 60 seconds. The vacuum provided by the vacuum pump 14 can be continuous or pulsed. A continuous vacuum is preferred for the reason that it requires fewer components than does a pulsed vacuum. It is preferred that the vacuum applied not cause irreversible damage to the skin. It is preferred that the vacuum applied not produce bruises and discolorations of the skin that persist for several days. It is also preferred that the level of vacuum applied and duration of application of vacuum not be so excessive that it causes the dermis to separate from the epidermis, which results in the formation of a blister filled with fluid. The vacuum pump feature offers significant advantages over the method and apparatus described in U. S. Patent No. 5,320,607, in which a sealed vacuum chamber in a state of preexisting reduced pressure is used. The use of a vacuum pump provides the user with greater control of blood extraction conditions than does a sealed vacuum chamber in a state of preexisting reduced pressure. For example, if the vacuum is insufficient, energy can be provided to the vacuum pump to bring about a higher level of vacuum, thereby providing greater suction. The lancing assembly 16 comprises at least one lancet. Standard lancets can be used in the lancing assembly of this invention. Narrow gauge (28 to 30 gauge) lancets are preferred. Lancets suitable for this invention can be made from metal or plastic. Lancets suitable for this invention can have single points or multiple points. The depth of penetration of the lancet preferably ranges from about 0.4 to about 2.5 mm, more preferably from about 0.4 to about 1.6 mm. The length of the lancet or lancets preferably ranges from about 1 mm to about 5 mm. The lancing assembly is preferably located so that the user can easily replace used lancets. The lancet of the lancing assembly 16 can be cocked manually or automatically, e. g., by means of a vacuum-actuated piston or diaphragm. The lancet of the lancing assembly 16 can be triggered manually or automatically, e. g., by means of a vacuum-actuated piston or diaphragm. Lancing assemblies are well-known in the art. Representative examples of lancing assemblies suitable for this invention are described in U. S. Patent Nos. Re. 32,922, 4,203,446, 4,990,154, and 5,487,748, all of which are incorporated herein by reference. A particularly suitable lancing assembly for this invention is described in U. S. Patent No. Re. 32,922. However, any lancing assembly selected should operate in conjunction with the other features of the apparatus of this invention. For example, if a vacuum is employed, the lancing assembly must be designed so that a vacuum can be formed and drawn through the assembly. The lancing assembly can be designed to allow automatic cocking and automatic triggering of the lancet. While conventional lancing assemblies are suitable for use in this invention, a lancing assembly that utilizes differential gas pressure to thrust a lancet into skin tissue has been developed for use with this invention. As used herein, the expression "differential gas pressure" means the difference in gas pressure between a gas source at a high pressure, e. g., ambient air or pressurized air, and a gas source at a low pressure, e. g., air within a vacuum. In any event, the pressure of a gas source at high pressure exceeds the pressure of a gas source at low pressure. FIGS. 11 , 12, 13, and 14 illustrate an embodiment of a lancing assembly suitable for use in this invention. In this embodiment, the gas is air. However, it should be noted that other gases, e. g., nitrogen, carbon dioxide, can be used in place of air for the gas source at low pressure, the gas source at high pressure, or both. The lancing assembly 60 of this embodiment comprises a housing 62, a piston 64 having a lancet holder 66, a lancet assembly 67 comprising a lancet 67a inserted into a body 67b, a piston biasing means 68, which, in this embodiment, is a return spring, and a cap 70. The housing 62 has a manifold 72 into which a three-way valve 74 can be fitted. See FIGS. 13 and 14 for manner of positioning the three-way valve 74 in the manifold 72. The three-way valve 74 selectively allows air from a source external to the housing 62 to pass through an inlet port 76 to a bore port 78, thereby causing the level of pressure in the bore 80 to increase. The increased pressure in the bore 80 causes the piston 64 to be thrust toward the target skin tissue while simultaneously compressing the return spring 68. The piston 64 is halted by the cap 70 or by another structure designed to limit the penetration depth of the lancet 67a in the skin. Such other structure can be a glucose detector in the form of a test strip, which will be described later, or a lancet stop, such as that designated by reference numeral 39 in FIG. 2. The three-way valve 74 then directs the air in the bore 80 to flow out through an exit port 82 to a source of low-pressure air, e. g., an evacuated air cavity in the apparatus, thereby causing the level of pressure in the bore 80 to decrease, and consequently allowing the return spring 68 to force the piston 64 back to its pre-thrust position in the bore 80. Proper sizing of the components is needed to satisfy both the dimensional limitations of the apparatus and the performance requirements of the lancing process, as explained further below. The lancing assembly of this invention occupies no more space than a conventional spring-powered device and typically requires less distance for the lancet to travel. The bore 80, typically cylindrical in shape, is the chamber in which differential air pressure is generated to thrust the piston 64 toward the target skin tissue. The bore 80 also functions to guide the piston 64 toward the target skin tissue, while providing a low-friction pneumatic seal against o-ring 84. The o-ring 84 is desirable for preventing high-pressure air from leaking out of the bore 80 during the lancing procedure, because the leakage of high-pressure air will decrease the level of air pressure in the bore 80, with the result that the thrusting speed of the piston 64 would be reduced. The manifold 72 is shaped to fit the three-way valve 74, which selectively connects bore port 78 to either inlet port 76 or exit port 82 to direct the flow of air to or from the bore 80. The exit port 82 is typically plumbed to a source of low-pressure air. The inlet port 76 is typically plumbed to a source of air pressure higher than that of the low- pressure air source. The ports 76, 78, and 82 are positioned to communicate with corresponding ports of the three-way valve 74, and are preferably sized to cause less flow resistance than the ports on the three-way valve 74. The piston 64 is the moving component of the lancing assembly 60. It is preferably cylindrical in shape, and has a lancet holder 66 and a circumferential gland 83 for a standard o-ring 84. The lancet holder 66 is designed to securely mount a disposable lancet assembly 67, which is inserted by the user in the same manner as is used with a conventional lancing device. The lancet assembly 67 comprises a lancet 67a, which is inserted into a molded plastic body 67b. The function of the o-ring 84 is to act as a seal to maintain air pressure in the bore 80 during lancing. The o-ring should cause negligible sliding friction force along the bore 80 (negligible compared to pressure forces acting on the piston 64). The length of the shaft 64a of the piston 64 is chosen to provide a desired stroke distance, typically 5 mm to 25 mm. The major dimension of the top surface 64b of the piston 64, typically 5 mm to 10 mm in diameter for a cylindrically-shaped piston, is chosen to provide adequate surface area for pressure forces to thrust the piston 64 and the lancet assembly 67. The return spring 68, typically a metal helical spring, is compressed between the piston 64 and the cap 70. The spring 68 forces the piston 64 to its maximum depth in the bore 80 when substantially no differential air pressure exists in the bore 80. This action properly positions the piston 64 to begin the lancing process. This position of the piston 64 is the position in which the piston 64 is furthest away from the target skin tissue when the apparatus is placed against the target skin tissue. The spring 68 also retracts the lancet assembly 67 in the lancet holder 66 away from the target skin tissue at the end of the lancing process. The spring force must be sufficient to overcome the weight of the piston/lancet system plus the sliding friction of the o-ring 84. The cap 70 is securely positioned in the housing 62. The cap 70 properly positions the return spring 68 while providing sufficient radial clearance for the spring 68 to compress freely. The cap 70 has a passage 88 through which the lancet holder 66 can move. The cap 70 can also function to help guide the piston 64 toward the target skin tissue. FIGS. 15A, 15B, and 15C illustrate an installation of the lancing assembly of FIGS. 11 and 12 inside a hypothetical apparatus 91. The lancing assembly 60 is fixed inside a cavity 92 of the apparatus 91 and fitted with a three-way solenoid valve 74 and a standard disposable lancet assembly 93 as shown. The lancet assembly 93 comprises a lancet 93a, which is inserted into a molded plastic body 93b. The apparatus 91 has a lower passage 94 through which the lancet assembly 93 can move to form an unobstructed opening in the area of the skin "S" that is circumscribed by a circular opening 94a (shown by dashed line) in the lower passage. A side port 95 on a wall 96 of the apparatus 91 connects inlet port 76 on the lancing assembly 60 to ambient air surrounding the apparatus 91. The apparatus 91 also has a vacuum source 97 to maintain the air pressure in the cavity 92 at the level at which the apparatus operates, and a voltage source 98 to selectively activate the three-way solenoid valve 74. With voltage off, the three-way solenoid valve 74 connects the bore 80 of the lancing assembly 60 with the cavity 92 via exit port 82, causing the piston 64 to experience no differential air pressure. In the "Ready" mode (FIG. 15A), the lower passage 94 of the apparatus 91 is placed across the target skin. The vacuum pressure of the apparatus reaches operational level P v , which is substantially less than ambient pressure P a (e. g., P v = -7.5 psig, P a = 0 psig). The target skin is partially drawn into the lower passage 94 by vacuum pressure P v . The voltage of the three-way solenoid valve 74 is initially off, thereby preventing ambient air from entering the lancing assembly 60, allowing the return spring 68 to maintain the lancet 93a at its maximum distance (e. g., 10 mm) from the skin. In the "Lance" mode (FIG. 15B), the three-way solenoid valve 74 is activated by the voltage source 98, which allows ambient air to flow continuously through the side port 95 of the apparatus 91 through the inlet port 76 and then through the bore port 78 into the bore 80 of the lancing assembly 60. The flow of ambient air increases the air pressure in the bore 80, causing a differential air pressure to act on the piston 64. The differential air pressure acting on the piston 64 rapidly increases and overcomes the opposing force of the return spring 68 and the friction of the o-ring 84, causing the combined mass of the piston 64 and lancet assembly 93 (e. g., 1.5 grams) to thrust toward the target skin. The lancet 93a contacts the skin in a short period of time (e.g., 6 msec) and reaches sufficient speed (e.g., 3.5 m/sec) to form an opening in the skin and to penetrate to a specified depth (e. g., 1.5 mm). The opening in the skin is complete when the thrusting motion of the lancet assembly 93 is halted by some halting means. Suitable means for halting the lancet assembly 93 include, but are not limited to, the cap 70 within the lancing assembly 60, which, in effect, limits the stroke distance of the piston 64, and a lancet stop, as will be described in FIG. 20. In the "Return" mode (FIG. 15C), the lancet 93a begins retracting from the skin when the voltage of the solenoid is shut off, which occurs after a predefined dwell time (e. g., 10 msec). With voltage off, the three-way solenoid valve 74 reconnects the bore 80 to exit port 82 in the lancing assembly 60 via the bore port 78, causing air from the bore 80 to vent quickly (e.g., 15 msec) through the three-way solenoid valve 74 and out through exit port 82 into the cavity 92, which contains low-pressure air, provided in the apparatus by the vacuum source 97. During venting, the compressed return spring 68 overcomes the combined force of the differential air pressure and the friction of the o-ring 84 to move the piston 64 and the lancet assembly 93 back to the starting position. The lancing cycle, which requires a total of 25 msec in this hypothetical apparatus, is then complete. The solenoid is driven by the voltage system of the apparatus. Each time the voltage is turned on and then turned off (i. e., one pulse), the three-way solenoid valve 74 switches internally, first directing flow of air into the lancing assembly 60 and then away from the lancing assembly 60. This switching causes the lancet to be thrust into the target skin tissue, then to be retracted away from the target skin tissue. By pulsing the solenoid repeatedly with voltage, the lancing process is repeated. This feature has been termed "repetitive lancing." The resulting opening formed in the skin is similar to that achieved with conventional lancing devices; such an opening is capable of allowing a volume of biological fluid (e.g., 3 μL capillary blood) to be sampled for analysis. The lancing process illustrated in FIGS. 15A, 15B, 15C can be repeated as many times as desired using the same lancet and without disturbing the device or target skin. With the skin still held in place by vacuum suction, the solenoid voltage can be pulsed as needed to lance the target area more than one time. Repetitive lancing has two potential benefits. First, it can be coordinated with an indexing system in the apparatus to lance a matrix of sites on the target skin for additional access to biological fluid. Second, it can increase the lancing success rate at or near a single site, by sequentially lancing into the skin until the desired amount of blood is obtained. FIGS. 16 and 17 illustrate another embodiment of the lancing assembly. In these figures, prime reference numerals (i. e., reference numerals 60', 62', 64', 64a', 64b', 66', 70', 72', 76', 78', 80', 82', 88') indicate components that are identical or at least substantially similar to components designated by the same reference numerals, but with no prime marking (i. e., reference numerals 60, 62, 64, 66, 70, 72, 76, 78, 80, 82, 88) in FIGS. 11 and 12. In FIGS. 16 and 17, bellows 89, typically a cylindrical molded elastomer, functions as both the pneumatic seal for bore 80' and the means for biasing piston 64'. The bellows 89 effectively replaces the o-ring seal 84 and the return spring 68 shown in FIGS. 11 and 12. To accommodate the bellows 89, the shaft 64a' of the piston 64' must have a radial cross-section dimension sufficiently smaller than that of the bore 80' to provide sufficient clearance for the bellows 89. A plate 90 fastens and seals the bellows 89 to the shaft 64a' of the piston 64', and provides a means of guiding the piston 64' through the bore 80'. A cap 70' and a housing 62' are shaped to fasten and seal the base of the bellows 89 as shown. This embodiment can be used in a manner identical to the embodiment shown in FIGS. 11 , 12, 13, 14, 15A, 15B, and 15C. It is clear that the embodiment employing the bellows 89 offers the potential advantage of reduced sliding friction when compared to the embodiment employing the o-ring 84. The bellows does not rub against the surface of the bore in the manner that the o- ring does; therefore, the bellows may result in reduced friction force. The friction force has the undesired effect of reducing the speed of the piston. It is also clear that the bellows requires less dimensional tolerance to be accommodated in the bore 80' than is required to accommodate the o-ring 84 in the bore 80. The bellows does not need to be precisely fitted into the bore, as does the o- ring. If the bore fits too tightly around the o-ring, then excessive sliding friction may result. If the bore fits too loosely around the o-ring, then excessive air leakage may result. By using the bellows in place of the o-ring, the manufacturing tolerances in the bore can be relaxed, with the result that manufacturing costs will be reduced and fewer parts will be rejected. The bellows 89 is preferably made of a material having sufficient stiffness and sufficient flexibility so that the bellows can perform the following functions: (1 ) act as a seal; (2) resist radial collapse under pressure; (3) allow the lancing assembly to retract to its initial pre-thrust position after the thrusting step; and (4) have its force overcome by differential gas pressure during operation. FIGS. 18 and 19 illustrate another embodiment of the lancing assembly. In these figures, double prime reference numerals (i. e., reference numerals 60", 62", 64", 64a", 64b", 66", 68", 70", 72", 76", 78", 80", 82", 88") indicate components that are identical or at least substantially similar to components designated by the same reference numerals, but with no prime marking (i. e., reference numerals 60, 62, 64, 66, 70, 72, 76, 78, 80, 82, 88) in FIGS. 11 and 12. In FIGS. 18 and 19, a diaphragm 84a, typically a molded elastomer, functions as the pneumatic seal for bore 80". The diaphragm 84a, in effect, replaces the o-ring seal 84 shown in FIGS. 11 and 12. The diaphragm 84a is fixed to the housing 62" and to the shaft 64a" of the piston 64" and can flex within the bore 80" when the shaft 64a" of the piston 64" moves axially in the bore 80". To accommodate the diaphragm 84a, the shaft 64a" of the piston 64" must have a radial cross-section dimension sufficiently smaller than that of the bore 80" to provide sufficient clearance for the diaphragm 84a. In addition, the housing 62" and the top 62a" of the housing must have assembly features to which the diaphragm 84a can be installed. The assembly features must also effectively seal the diaphragm 84a between the housing 62" and the top 62a" of the housing. The diaphragm 84a is preferably fastened to the shaft 64a" of the piston 64" by means of a fastener 83a. This embodiment can be operated in a manner identical to that of the embodiment shown in FIGS. 11 -17. The diaphragm 84a is preferably made of a material having sufficient strength and flexibility to perform the following functions: (1 ) act as a seal; (2) resist rupture under pressure during operation of the lancing assembly; (3) allow the lancing assembly to thrust a lancet into the skin of a patient; and (3) allow the lancing assembly to retract to its initial pre-thrust position after the thrusting step. The components of the lancing assemblies in FIGS. 11 -19 must be of a shape and size to conform with the dimensional envelope available for the lancing assembly. Proper design of the components is also an important factor in achieving acceptable lancing results in the skin. Other important factors are the performance of the three-way valve (i. e., valve flow resistance and switching time) and the air pressure environment in which the lancing assembly operates, as discussed below. The components for constructing the lancing assembly are commercially available, and one of ordinary skill in the art would be expected to have sufficient ability to select the proper components from commercially available sources. Lancing results are believed to be influenced by three main parameters: (1 ) lancet speed during impact with the skin, (2) inertial mass of the lancet/piston combination of the lancing assembly, and (3) shape and size of the lancet needle. The third parameter is not addressed by the lancing assembly of this invention because the assembly is expected to function with most commercially available lancet assemblies, such as the "BD ULTRA-FINE" (Becton-Dickinson) and the "ULTRATLC" (MediSense) brands. The first and second parameters are greatly affected by the geometrical shapes and weights of the components in the lancing assembly, although the precise influence of lancet speed and inertial mass on lancing performance are not well understood. However, good lancing performance has been observed with conventional devices, which have an inertial mass typically from 1.0 gram to 2.0 grams and deliver a peak lancet speed ranging from 3 m/sec to 5 m/sec. A general mathematical expression that relates the lancet speed to the design of the lancing assembly and the pressure environment can be formulated from physical laws as follows: M * a(t) = A * [ P c (t) - P v (t) ] - K s * [ x(t) + X s ] - Ff (t) where t = elapsed time M = total inertial mass (piston + lancet assembly) a(t) = translational acceleration of the lancet at time = t Pcrø = air pressure acting on the top surface of the piston at time = t P v (t) = air pressure opposing the action of the piston at time = t A projected surface area of the piston acted upon by P c (t) and P v (t) K s = spring rate constant of the return spring x(t) = translational displacement of the lancet at time = t Xs = initial displacement of the return spring Ff(t) = friction force of the piston seal at time = t Pc(t) - Pv(t) = differential pressure level which accelerates the piston at time = t Solution of the foregoing expression for lancet displacement (x) vs. time (t), from which lancet speed as a function of time can be determined, requires many auxiliary equations in the field of thermodynamics and compressible flow, which incorporate design details of the invention and the three-way valve. In general, the lancet speed (U p ) at the time of impact on the skin can be expressed in terms of the following variables: U p = F [ A, M, S, X p , K s , Xs, C v , Dt v> V c , V v , P a , P v , T a , Ff ] where A = effective surface area of the piston on which air pressure acts M = total inertial mass (piston + lancet assembly) S = stroke distance of the piston Xp = lancet displacement when impact with skin occurs (X p < S) K s = spring rate constant of the return spring X s = initial displacement of the return spring C v = flow coefficient of the three-way valve when activated Dt v = switching time of the three-way valve (time to fully activate) V c = initial air volume between the piston and three-way valve V v = initial cavity volume of the apparatus (i. e., measured volume of the cavity prior to actuation of the lancet) P a = pressure level of the high-pressure air source P v = initial pressure level of the cavity of the apparatus (i. e., measured pressure of low pressure air source prior to actuation of the lancet) T a = air temperature level Ff = friction force profile of the piston seal (typically varies as a function of the displacement of the piston) Maximizing the lancet speed within a specified stroke distance of the piston (S) is accomplished by selecting a three-way valve with high flow coefficient (C v ) and rapid switching time (Dt v ), by optimizing the surface area of the piston (A) and initial air volume between the piston and three-way valve (V c ), by minimizing the total inertial mass (M), the spring force (K s , X s ), and the friction force profile of the piston seal (Ff), by ensuring adequate initial cavity volume (V v ), and by applying as much pressure differential (P a - P v ) as permitted by the apparatus. The lancing assembly that utilizes differential gas pressure offers several advantages over conventional lancing assemblies. The advantages are brought about by using differential gas pressure rather than a compressed spring to thrust the lancet into the skin. One advantage is that the lancet does not need to be manually cocked by the user before use. This simplifies usage and permits sequential lancing of the target skin to provide greater access to blood. Cocking is not required because the gas providing differential gas pressure is vented from the lancing assembly after use, thereby allowing the piston biasing means to force the lancet back to its original position. Another advantage is that the lancing assembly does not need to be mechanically triggered. This simplifies the design of the device and protects against accidental triggering by the user if the device is mishandled. A separate triggering mechanism is not required because the differential gas pressure functions to both initiate and execute the lancing process. Still another advantage is that the lancing assembly fully retracts the lancet when lancing is not in progress. This minimizes exposure of the user to the sharp lancet when handling the device in preparation for use or after use. Full retraction of the lancet is accomplished by the piston biasing means after the gas that provided the differential gas pressure has been vented from the lancing assembly. Returning to FIG. 1 , the vacuum pump 14 is connected to the lancing assembly 16 by an evacuation tube 24. The air that is evacuated from the lancing assembly 16 by the vacuum pump 14 is removed via the evacuation tube 24. The evacuation tube 24 is typically made from a polymeric material. A check valve 26 is placed between the vacuum pump 14 and the lancing assembly 16 at a point in the evacuation tube 24 to prevent air removed from the lancing assembly 16 by the vacuum pump 14 from flowing back to the lancing assembly 16 and adversely affecting the vacuum. A source of power for the vacuum pump 14 can be disposed within the housing 12. A source of power suitable for the device of this invention is a battery 18. Alternatively, an external source of power can be used to operate the vacuum pump 14. The power source is actuated by the electronics 20, which, in turn, is actuated by the switch 22. The electronics 20 may incorporate a microprocessor or microcontroller. The function of the electronics 20 is to switch power on and off to operate the various components in the apparatus. These components include, but are not limited to, the vacuum pump 14. The electronics 20 can also be use to switch power on and off to operate components in alternative embodiments, e. g., heating elements, lancets, indicating devices, and valves. Electronics suitable for this invention is the "TATTLETALE MODEL 5F" controller/data logger, commercially available from Onset Computer Corporation, 536 MacArthur Blvd. P. O. Box 3450, Pocasset, Massachusetts 02559-3450. Auxiliary electronic devices, such as power transistors, pressure monitors, and OP-Amps (operational amplifiers), may also be required in order to provide an interface between the controller and the operational components. All electronics required for this invention are well-known to one of ordinary skill in the art and are commercially available. Auxiliary electronic devices suitable for use in this invention include the following components: FIG. 3 illustrates by way of a block diagram how the foregoing electronic components can be arranged to carry out the method of the present invention. Operation of the blood extraction device 10 will now be described. Referring now to FIGS. 1 , 2 and 3, the nosepiece 30 of the lancing assembly 16 is applied to the surface of the skin, designated herein by the letter "S". The end of the nosepiece 30 that contacts the skin is equipped with a seal 32. The purpose of the seal 32 is to prevent air from leaking into blood extraction chamber 34, so that the vacuum pump 14 can provide sufficient suction action for increasing the availability of blood to the area of the skin from which the sample is to be extracted, stretching the skin, and extracting the sample of blood from the unobstructed opening in the skin. The seal 32 surrounds an opening 33 in the nosepiece 30. The opening 33 in the nosepiece allows communication between the surface of the skin and a blood extraction chamber 34 in the nosepiece 30. The seal 32 is preferably made of a rubber or an elastomeric material. FIG. 4 illustrates an alternative position for the seal 32. In FIG. 4, the seal is designated by the reference numeral 32'. The remaining parts of FIG. 4 are the same as those of FIG. 2, and , accordingly, retain the same reference numerals as were used in FIG. 2. It has been discovered that an improved design and construction of the nosepiece 30 can provide enhanced collection of blood from the unobstructed opening in the skin. In FIG. 2, it is shown that the interior walls of the nosepiece form a shape that is essentially cylindrical. While this design is capable of providing adequate performance in the method of this invention, it has been discovered that by changing the construction of the interior cavity of the nosepiece, collection of blood can be accelerated. A nosepiece assembly 3000 is illustrated in FIG. 32. The nosepiece assembly 3000 comprises a nosepiece 3001 and a seal 3002. The nosepiece 3001 comprises a lower base 3004 having an opening 3005 therein. Above the lower base 3004 is an upper base 3006 having an opening 3007 therein. The features of the exterior of the nosepiece, other than the lower base 3004 and the upper base 3006, are not critical to this invention, and one of ordinary skill in the art can design the exterior walls of the nosepiece in any manner that does not adversely affect the operation of the nosepiece of this invention. The features of the interior of the nosepiece, the lower base 3004, the upper base 3006, and, in some cases, the seal 3002 are critical and, consequently, they will be described in greater detail. An interior wall 3008 encloses a cavity 3010 of the nosepiece 3001. It is critical that the interior wall 3008 of the nosepiece 3001 be structured in such a manner that the opening 3007 in the upper base 3006 be of an equal or smaller area than the opening 3005 in the lower base 3004. It is desired that the area of the opening 3007 be reduced to as small of a size as possible, but not so small as to interfere with the collection of blood by a glucose monitor (see FIG. 2) or with the path of a lancet. An optional rim 3012 can surround the opening 3007 in the upper base 3006. There are several ways of causing the area of the opening 3007 to be less than the area of the opening 3005. As shown in FIG. 32, the interior wall 3008 can be tapered so as to bring about a reduction in the area of the opening 3007. The tapering can begin at any point along the interior wall 3008 of the nosepiece 3001. If the tapered portion runs all the way from the beginning of the tapered portion to the upper base 3006, the optional rim 3012 will have a depth of zero, and thus be eliminated from the nosepiece. Alternatively, the area of the opening 3007 can merely be made smaller than the area of the opening 3005, such as through the use of step-wise cylindrical sections. Ports 3014 and 3016 can be included in the nosepiece 3001 to give the cavity 3010 more exposure to a vacuum, if needed. In order to more accurately describe the construction of the nosepiece assembly 3000, reference points, designated by alphabetical letters, have been placed on FIG. 32 so that typical distances between these reference points can be disclosed. The optional rim 3012 has a depth designated by the line "ab". This depth typically ranges from 0 to about 1.5 mm, preferably from 0 to about 1.0 mm. The opening 3007 in the upper base 3006 has a major dimension designated by the line "cd". The area of the opening 3007 typically ranges from about 1 to about 500 mm 2 , preferably from about 1 to about 150 mm 2 . The opening 3005 in the lower base 3004 has a major dimension designated by the line "ef". The area of the opening 3005 typically ranges from about 10 to about 500 mm 2 , preferably from about 50 to about 150 mm 2 . The distance from the lowermost point of the rim 3012 to to lowermost point of the seal 3002 (hereinafter "rim-to-seal distance") is designated by the line "bg" This distance typically ranges from about 1.5 to about 8.0 mm, preferably from about 3 to about 6 mm. It is preferred that the distance be selected so that the skin, when stretched into the nosepiece 3001 , comes as close as possible to the rim 3012 or the upper base 3006 of the nosepiece 3001. If the rim 3012 is not present, the point "d" will be located at the level of the upper base 3006. The thickness of the seal 3002 is represented by the line "eh". The width of the sealing surface and the width of the sealed surface of the lower base 3004 are designated by the line "hj". One of ordinary skill in the art would have sufficient expertise to optimize the dimensions of the nosepiece without undue experimentation. Additional details regarding the nosepiece 3001 and the seal 3002 are dealt with in the examples. This improved nosepiece has several advantages. The improved design and construction of the nosepiece can provide enhanced collection of blood from the unobstructed opening in the skin. In addition, The nosepiece brings about a better seal to the body than do the nosepieces previously used. A better seal reduces the amount of vacuum leakage, with the result that a less expensive vacuum pump can be used. In addition, the improved nosepiece allows a seal to be maintained on those individuals having excessively hairy skin. A particularly preferred type of nosepiece may have a seal of the type shown in FIGS. 42A and 42B in cross section, referred to hereinafter as a flex seal. The flex seal contacts a larger area of skin than does a planar seal. The flex seal can then cause more skin to be brought into the internal space of the nosepiece when vacuum is applied than can a planar seal. The flex seal can be made out of a silicone, 40A durometer. The flex seal 3020 can be attached to the nosepiece 3022 by a mechanical attachment 3024 or by an adhesive. The portion 3026 of the flex seal that is not attached to the nosepiece 3022 is capable of moving between a first position, as shown in FIG. 42A, and a second position, as shown in FIG. 42B. In the first position, the unattached portion 3026 of the flex seal 3020 depends from the lower base 3028 of the nosepiece 3022 as shown in FIGS. 42A. In the second position, the unattached portion 3026 of the flex seal 3020 contacts the lower base 3028 of the nosepiece 3022 such that one major surface of the unattached portion of the seal is in face-to-face contact with the lower base 3028 of the nosepiece as shown in FIG. 42B. The flex seal is made of a material having a coefficient of friction that reduces the tendency of skin in contact with it to slide. The seal should be sufficiently flexible so that it can move between the first position and the second position and sufficiently stiff to hold the skin in an immovable position. The opening 3030 in the flex seal has an area greater than the area of the opening 3032 in the lower base 3028 of the nosepiece 3022, when the flex seal is in the first position, as shown in FIG. 42A. In operation, the flex seal, is placed against the skin "S" of the patient. The area of skin contacted by the flex seal is greater than the area of the opening in the lower base of the nosepiece. Consequently, the volume of skin lifted into the nosepiece is greater than the volume of skin that would have been lifted into the nosepiece with a planar seal. Thus, the flex seal would be beneficial for a patient having below normal skin flexibility. The switch 22 is actuated, typically by being pressed, thereby activating the electronics 20, which starts the vacuum pump 14. The vacuum pump 14 then provides a suction action. The suction action of the vacuum pump 14 causes the skin circumscribed by the seal 32 to become engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin up to opening 33. After an appropriate period of time, which is typically pre-set by the programmer of the electronics, the lancing assembly 16 is triggered, thereby causing the lancet 36 to penetrate the skin that has risen up to the opening 33 and that is engorged with blood. The lancet 36 is preferably triggered automatically, by a solenoid valve 38 that causes a vacuum-actuated piston (not shown) to trigger the lancet 36. The lancet 36 is then retracted, preferably automatically. Thereupon, the blood flows out of the unobstructed opening resulting from the lancet 36, and, aided by the vacuum generated by the vacuum pump 14, is collected. When sufficient blood has been collected or a pre-set time interval has passed, the electronics 20 causes the vacuum pump 14 to stop. The device 10 can then be removed from the surface of the skin after another solenoid valve (not shown because it is hidden under solenoid valve 38) is opened to vent the vacuum to allow ease of removal of the device from the surface of the skin. Solenoid valves suitable for use with the apparatus described herein are commercially available from The Lee Company, Essex, CT and have the part number LHDA0511111 H. The blood is preferably directly collected on the application zone of a glucose detector, e. g., a reflectance strip or biosensor. The blood can then be used as the sample for a determination of glucose concentration in blood. Alternatively, the blood can be collected by other collection devices, such as , for example, a capillary tube or absorbent paper. The apparatus of the present invention can include a glucose detector for analyzing the blood sample extracted by the apparatus. Glucose detectors are well-known in the art. With respect to glucose monitoring, there are two major categories of glucose detectors - reflectometers and biosensors. Representative examples of reflectometers suitable for this invention are described in U. S. Patent No. 4,627,445, incorporated herein by reference. Representative examples of biosensors suitable for this invention are described in U. S. Patent No. 5,509,410, incorporated herein by reference. The glucose detector is preferably disposed in the nosepiece 30 of the lancing assembly 16. The glucose detector must be located at a position sufficiently close to the site of blood extraction so that the quantity of extracted blood collected will be sufficient to carry out a standard glucose monitoring test. Typically, this distance will preferably be no more than 5 mm from the site of blood extraction, more preferably no more than 3 mm from the site of blood extraction, most preferably no more than 1 mm from the site of blood extraction. Alternatively, the glucose detector may be maintained at a distance greater than 5 mm from the site of blood extraction until shortly after the lancet has been triggered, preferably about 50 milliseconds but at least long enough to allow the lancet to be retracted. If the glucose detector is so positioned, it may then be triggered, for example by a solenoid valve that causes a vacuum actuated piston to trigger the glucose detector. Other triggering mechanisms may also be used. The triggering action propels the glucose detector towards the skin, preferably no more than 5 mm from the site of blood extraction, more preferably no more than 3 mm from the site of blood extraction, most preferably no more than 1 mm from the site of blood extraction. Care must be taken in the placement of the glucose detector so that the detector does not adversely affect the vacuum, when a vacuum is employed to aid in the extraction of blood. In addition, the glucose detector 40 should be modified, if necessary, so that the blood collected in the collection zone of the glucose detector is capable of being used to activate the glucose detector. FIG. 2 also illustrates a manner for disposing a glucose detector 40 in the nosepiece 30 of the lancing assembly 16. One embodiment of the glucose detector 40 of this invention involves a multiple-layer element comprising: (a) a layer capable of receiving blood and transporting the blood received by means of chemically aided wicking; (b) a layer capable of detecting the presence of analyte or measuring the amount of analyte in blood; and (c) a layer that can be placed in contact with a meter, the meter- contactable layer overlying the blood-transporting layer, said layer (a) capable of transporting blood to said layer (b). One preferred embodiment of the glucose detector 40 of this invention involves a multiple-layer element, which comprises: (a) a covering layer having an opening therein; (b) a layer, overlying the covering layer, capable of receiving blood through the opening in the covering layer and transporting blood by means of chemically aided wicking; (c) a layer that can be placed in contact with a meter, the meter- contactable layer overlying the blood-transporting layer; and (d) a layer capable of detecting the presence of analyte or measuring the amount of analyte in blood, which layer is disposed between the covering layer and the meter-contactable layer and is capable of receiving blood from the blood- transporting layer. FIGS. 21 A and 21 B illustrate the aforementioned preferred embodiment of the multiple-layer element of this invention. During the course of discussing this embodiment, a discussion of the embodiment that does not require a covering layer will also be discussed. The multiple-layer element 1100 comprises a covering layer 1102 having an opening 1104 therein. To one major surface 1106 of covering layer 1102 is adhered a layer 1108 capable of transporting blood by means of chemically aided wicking to a detecting layer 1110. The other major surface 1112 of the covering layer 1102 is the surface that comes in close proximity to or may even contact the skin. Overlying layer 1110 is a meter-contactable layer 1114 having an opening 1116 therein. The opening 1104 in the covering layer 1102 and the opening 1116 in the meter-contactable layer 1114 are aligned so that a lancet can pass through the opening 1104 and through the opening 1116 to pierce the skin. The blood- transporting layer 1108 can be designed to allow the lancet to pass through it or it can be positioned so that the lancet need not pass through it. The opening 1104 in the covering layer 1102 allows the blood-transporting layer 1108 to take up blood emerging from the opening in the skin formed by the lancet so that blood from that opening in the skin can be transported by means of a chemically aided wicking action to the detecting layer 1110. The detecting layer 1110 can be disposed on a major surface of the covering layer 1102 or on a major surface of the meter-contactable layer 1114. The detecting layer 1110 comprises a layer or layers of chemicals, e. g., an enzyme, capable of reacting with an analyte in a biological fluid to produce either a measurable electrical response or a measurable optical response. U. S. Patent Nos. 4,545,382; 4,711 ,245; and 5,682,884; all of which are incorporated herein by reference, describe detecting layers capable of generating a measurable electrical signal in response to glucose in blood. U. S. Patent Nos. 4,935,346 and 4,929,545, both of which are incorporated herein by reference, describe detecting layers capable of producing a measurable change in reflectance in response to glucose in blood. An example of a detecting layer is described in U. S. Patent No. 5,682,884. The detecting layer described in U. S. Patent No. 5,682,884 comprises a first conductor and a second conductor extending along a support and further comprises a means for connection to readout circuitry. An active electrode, positioned to contact the liquid blood sample and the first conductor, comprises a deposit of an enzyme capable of catalyzing a reaction involving the analyte compound, e. g., glucose, in the liquid blood sample. Electrons are transferred between the enzyme-catalyzed reaction and the first conductor to create the current. A reference electrode is positioned to contact the liquid blood sample and the second conductor. The covering layer 1102 is preferably formed from a hydrophobic material. The covering layer is preferably sufficiently flexible to conform to the remaining layers of the multiple-layer element. Representative examples of materials that are suitable for preparing the covering layer include, but are not limited to, polymeric materials, such as polyesters, polyimides, polyethylenes, polypropylenes, polycarbonates, polyacrylics, and combinations thereof. The thickness of the covering layer 1102 is not critical, but preferably ranges from about 0.005 mm to about 2.0 mm. The surface dimensions of this layer are not critical, but the major surface dimension preferably ranges from about 5 mm to about 60 mm and the minor surface dimension preferably ranges from about 2 mm to about 30 mm. The layer is shown as being elongated and rectangular, but other shapes are also suitable, e. g., circular, elliptical, triangular, square, and other shapes. The size of the opening 1104 in the covering layer 1102 must be sufficiently large to allow a lancet to pass therethrough into the skin of the patient. It is preferred that the opening 1104 be sufficiently large for a commercially available lancet to be used. Because commercially available lancet assemblies vary in how precisely the lancet is centered within the body of the lancet assembly, the opening 1104 in the covering layer 1102 is preferably sufficiently large to allow passage of the lancet, but not so large that it compromises the strength of the covering layer. Typically, the opening 1104 is no larger than one-half to three-quarters of the width of the covering layer 1102. Although the embodiment in FIGS. 21 A and 21 B displays a covering layer, it is possible, but not preferred, to dispense with the covering layer entirely. In embodiments dispensing with the covering layer, the meter-contactable layer can have an opening therein through which the lancet can pass; alternatively, a sufficient amount of the meter-contactable layer can be trimmed such that a lancet will avoid striking the end of the meter-contactable layer prior to forming an opening in the skin. In this latter embodiment, the blood-transporting layer may or may not have an opening therein through which the lancet can pass. The blood-transporting layer 1108 is preferably made from polymeric material, cellulosic material, natural fibrous material, or an equivalent material. Representative examples of polymeric materials suitable for the blood-transporting layer of this invention include, but are not limited to, polymers comprising amide monomeric units, e. g., nylon, ester monomeric units, alkylene monomeric units, e. g., polypropylene, polyethylene, cellulosic monomeric units, and combinations thereof. The blood-transporting layer can be a mesh. The mesh is preferably constructed of finely woven strands of polymeric material; however, any woven or non-woven material may be used, provided that the blood-transporting layer transports the blood to the detecting layer 1110 before the blood evaporates or clots. A fine mesh that is suitable for the multiple-layer element of this invention has a percent open area of from about 40 to about 45%, a mesh count of from about 95 to about 115 fibers per cm, a fiber diameter of from about 20 to about 40 μm, and a thickness of from about 40 to about 60 μm. A particularly preferred mesh is NY64 HC mesh, available from Sefar (formerly ZBF), CH-8803, Ruschlikon, Switzerland. A coarse mesh that is suitable for the multiple-layer element of this invention has a percent open area of from about 50 to about 55%, a mesh count of from about 45 to about 55 fibers per cm, a fiber diameter of from about 55 to about 65 μm, and a thickness of from about 100 to about 1000 μm. A preferred mesh is NY151 HC mesh, available from Sefar (formerly ZBF), CH-8803, Ruschlikon, Switzerland. Mesh characteristics are further described in U. S. Patent No. 5,628,890, incorporated herein by reference. The blood-transporting layer 1108 transports blood by means of a chemically aided wicking action. As used herein, the expression "chemically aided wicking action" refers to either: (a) the flow of fluid along a material wherein the nature of the material itself is hydrophilic, such as, for example, cellulose; (b) the flow of fluid along a material wherein at least one chemical substance is applied to the surface of the material, such as, for example, nylon coated with surfactant; (c) the flow of fluid along a material that has been rendered hydrophilic by means of a chemical or physical process, such as, for example, treatment of polyester by means of corona discharge treatment, plasma treatment, flame treatment, or the like. The purpose of the at least one chemical substance applied to the surface of the material of the blood-transporting layer is to promote the flow of fluid along the surface of the material. Chemical substances suitable for the foregoing purpose belong to the class of compounds commonly referred to as surfactants. Surfactants reduce the surface tension of the surface upon which they are coated and allow the coated surface to attract rather than repel fluids. A commercially available surfactant suitable for use in this invention is a fluorochemical surfactant having the trade designation "FC 170C FLUORAD", available from Minnesota Mining and Manufacturing Company, St. Paul, Minnesota. This surfactant is a solution of a fluoroaliphatic oxyethylene adduct, lower polyethylene glycols, 1 ,4-dioxane, and water. It has been found that approximately 1 to 10 μg surfactant per mg of blood- transporting layer is preferred. The preferred surfactant loading may vary depending upon the nature of the material of the blood-transporting layer and the surfactant used. The preferred amount can be determined empirically by observing flow of sample along the blood-transporting layer with different levels of surfactant loading. The surfactant may not be necessary if the mesh is made of hydrophilic material. The blood-transporting layer 1108 is capable of allowing a sufficient amount of blood to uniformly flow through it at a rate sufficiently great that a sufficient amount of blood, e. g., 0.1 to 10 μl, preferably up to 2 μl, more preferably up to 1 μl, reaches the detecting layer 1110 before evaporation causes the size of the sample to be inadequate to provide a reading of analyte level within a reasonable time, e. g., up to five minutes. The blood-transporting layer 1108 can be adhered to the covering layer 1102 by means of hot melt adhesive on the major surface of the covering layer that faces the meter-contactable layer 1114. The blood-transporting layer 1108 can have a small opening formed in it, aligned with the path of the lancet and aligned with the openings in the covering layer 1102 and the meter- contactable layer 1114, whereby the possibility of the lancet striking a strand of mesh during the lancing operation is eliminated. The covering layer 1102 and the blood-transporting layer 1108 are preferably arranged in such a way that blood emerging from the opening in the skin is not impeded from reaching the blood-transporting layer by the covering layer. Arrangements for the covering layer 1102 and blood-transporting layer 1108 suitable for use in this invention can be seen in FIGS. 21 A, 21 B, 22, 23, 24, 25, 26A, 26B, and 27. It should be noted that FIG. 23 does not show a covering layer, but it should also be noted that FIG. 23 depicts the opposite side of the multiple- layer element of FIG. 22. As shown in FIGS. 21 A and 21 B, the multiple-layer element has an opening 1104 formed in the covering layer 1102 and an opening 1116 formed in the meter- contactable layer 1114. The blood-transporting layer 1108 is disposed between the covering layer 1102 and the meter-contactable layer 1114. In FIGS. 22, 23, 24, and 25, the blood-transporting layer 1108 is disposed directly over the opening 1104 in the covering layer 1102. In the detecting layer, electrical contacts are represented by the part having the reference numeral 1110a. In FIG. 13, the blood-transporting layer 1108 is disposed directly under the opening 1116 in the meter-contactable layer 1114. In FIGS. 22 and 23, the blood- transporting layer is a mesh having a relatively large number of openings per unit area. In FIG. 24, the blood-transporting layer is a mesh having a relatively small number of openings per unit area. In the embodiments shown in FIGS. 22, 23, and 24, there is the possibility that the lancet will hit one of the strands of mesh during the skin-opening step of the process. If a lancet hits one of the strands, the moving mass must have sufficient momentum to pierce the strand and the skin below it. The momentum of the moving mass is a function of the mass and the velocity of the moving components of the lancing assembly. The strength of the blood- transporting layer with respect to piercing will also determine the effectiveness of the lancing. The thickness and the material properties of the blood-transporting layer will determine its strength. It is preferred that the thickness and material properties of the mesh be such that a commercially available lancet can pierce the mesh. In FIG. 25, the blood-transporting layer 1108 is disposed between the covering layer 1102 and the meter-contactable layer 1114 and is disposed directly under the opening 1104 in the covering layer 1102; however, the blood- transporting layer 1108 also has an opening 1118 formed therein. In the embodiment shown in FIG. 15, there is no possibility that the lancet will hit one of the strands of mesh during the skin-opening step of the process. As shown in FIG. 26A, the meter-contactable layer 1114 has two openings 1116 and 1122 formed therein. The blood-transporting layer 1108 is offset from opening 1116 and directly over opening 1122. In this embodiment, the lancet passes through opening 1116 to form the opening in the skin. Then, some type of mechanical device, e. g., a spring, a solenoid, a pivot, or a four-bar linkage, causes the multiple-layer element to move a sufficient distance such that at least a portion of the blood-transporting layer 1108 is substantially directly over the opening formed in the skin, thereby minimizing the distance the blood needs to travel to reach the blood-transporting layer 1108 and at the same time eliminating the possibility of the lancet striking a strand of mesh during the lancing operation. The opening 1122 in the meter-contactable layer directly aligned with the blood- transporting layer 1108 can be used for application of vacuum to enhance the collection of blood. However, it should be noted that such an opening is optional, and can be dispensed with in other embodiments. See, for example, FIG. 26B, in which only one opening is formed in the meter-contactable layer. In FIG. 27, the blood-transporting layer 1108 abuts one end 1121 of the multiple-layer element. In the embodiment of FIG. 27, a lancet that passes through semi-circular opening 1104 can strike a strand of mesh during the lancing operation. The blood emerging from the opening formed in the skin has a minimal distance to travel to reach the blood-transporting layer 1108. Alternatively, after a lancet has formed an opening in the skin, the multiple-layer element can be moved in the manner described previously to facilitate taking up of blood by the blood- transporting layer 1108. The detecting layer 1110 preferably comprises an electrochemical detector, e. g., a biosensor, or an optical detector, e. g., a reflectance detector. The detecting layer 1110 is supported on either the covering layer 1102 or on the meter- contactable layer 1114. Detecting layers of the electrochemical type are preferably non-porous. Detecting layers of the optical type are preferably porous. It is preferred that the detecting layer be flexible, so that it will conform to whichever layer to which it is applied, the covering layer 1102 or the meter-contactable layer 1114. Detecting layers of the electrochemical type can be transparent or non-transparent. Detecting layers of the optical type are preferably reflective. The detecting layer 1110 contains the reagents required for the chemical reaction required to provide an indication of the concentration or presence of analyte. In the case of glucose monitoring, these reagents include, but are not limited to, ferrocene, ferricyanide, glucose oxidase, glucose dehydrogenase, and peroxidases. Detecting layers of the electrochemical type preferably comprise a member selected from the group consisting of carbon, platinum, gold, palladium, silver chloride, and silver. Detecting layers of the reflectance type preferably comprise a member selected from the group consisting of dyes and enzymes. As stated previously, a typical detecting layer comprises a first conductor and a second conductor extending along a support and further comprises a means for connection to readout circuitry. An active electrode, positioned to contact the liquid blood sample and the first conductor, comprises a deposit of an enzyme capable of catalyzing a reaction involving the analyte compound, e. g., glucose, in the liquid blood sample. Electrons are transferred between the enzyme-catalyzed reaction and the first conductor to create the current. A reference electrode is positioned to contact the liquid blood sample and the second conductor. In a preferred embodiment of a detecting layer for the multiple-layer element of this invention, an electron mediator, e. g., a ferrocene, is included in the active electrode deposit to effect the electron transfer. The compound being detected is glucose and the enzyme is glucose oxidase or glucose dehydrogenase. The active electrode and the reference electrode are coatings applied to the covering layer 1102 or to the meter-contactable layer 1114. For example, the active electrode is formed by printing (e. g., screen printing) an ink comprising a conductive compound, the enzyme, and the mediator, and the reference electrode is also formed by printing (e. g., screen printing). The means for connecting to the readout circuit are positioned toward one end of the covering layer 1102 or the meter-contactable layer 1114, and the electrodes are positioned remote from that end. Additional variations of the foregoing embodiment are described in the previously incorporated U. S. Patent No. 5,682,884. The meter-contactable layer 1114 is preferably made from a polymeric material. Representative examples of polymeric material suitable for preparing the meter-contactable layer include polymers comprising acrylic monomeric units, methacrylic monomeric units, acrylate monomeric units, methacrylate monomeric units, vinyl chloride monomeric units, and combinations of the foregoing. Other polymers suitable for preparing the meter-contactable layer include polyesters. The functions of the meter-contactable layer are to (1 ) provide a surface on which to print the detecting layer 1110, (2) provide alignment of the opening or openings in the multiple-layer element with the lancet, (3) provide contact of the multiple- layer element with the meter for the purpose of reading the signal from the detecting portion of the multiple-layer element, (4) provide a rigid layer so that the multiple-layer element can be easily picked up and placed in contact with the meter, and, in the case of a detector measuring an optical response, provide a surface to contact against a meter, which contains a light source and means for reading the glucose signal from the detecting layer. The size of the opening 1116 in the meter-contactable layer 1114 must be sufficiently large to allow a lancet to pass therethrough into the skin of the patient. It is preferred that the opening 1116 be sufficiently large for a commercially available lancet to be used. Because commercially available lancet assemblies vary in how precisely the lancet is centered within the body of the lancet assembly, the opening 1116 in the meter-contactable layer 1114 is preferably sufficiently large for passage of the lancet, but not so large that it compromises the strength of the meter-contactable layer. Typically, the opening 1116 is no larger than one-half to three-quarters of the width of the meter-contactable layer 1114. Although the meter-contactable layer 1114 shown in FIGS. 21 A and 21 B displays an opening 1116, it is possible, but not preferred, to dispense with the opening 1116, so long as a sufficient amount of the meter-contactable layer 1114 is trimmed such that a lancet will avoid striking the end of the meter-contactable layer prior to passing through the opening 1104 in the covering layer 1102. In this embodiment, the blood-transporting layer 1108 may or may not have an opening therein. The following table lists suitable ranges for the dimensions of the layers of the multiple-layer element of this invention. It is not intended that the dimensions of the layers of the multiple-layer element of this invention be limited to the ranges listed in the following table. The multiple-layer element is preferably sufficiently rigid so that it can be easily handled by the user. In the preferred embodiments, either the covering layer 1102 or the meter-contactable layer 1114 or both of these layers are made of a material that is sufficiently rigid to support the blood-transporting layer 1108 and the detecting layer 1110. The last two mentioned layers can be extremely flexible and of minimal rigidity. The porosity of the layers of the multiple-layer element is dependent upon the positioning and functionality of the layer. The covering layer 1102 and the meter-contactable layer 1114 are preferably sufficiently non-porous to form a well or chamber for the blood. The blood-transporting layer 1 108 is preferably sufficiently porous to allow blood to flow uniformly and rapidly therethrough to the detecting layer 1110. The porosity of the detecting layer is not critical; it can be porous or non-porous depending upon the design selected by the manufacturer. The surface dimensions, e. g., length, of the blood-transporting layer 1108 are preferably less than those of the layer on which the detecting layer 1110 is printed, so that in the case of electrochemical sensors, the electrical contacts 1110a on the detecting layer 1110 are exposed to facilitate insertion into the meter. The surface dimensions, e. g., length, of the meter-contactable layer 1114 are preferably larger than those of the covering layer 1102 so that electrical contacts, in the case of electrochemical sensors printed on the meter-contactable layer, are exposed for insertion into the meter. The opacity of the meter- contactable layer is not critical unless photometric detection is used. As stated previously, an optional overcoat layer 1123, as shown in FIG. 28, can be interposed between the covering layer 1102 and the meter-contactable layer 1114 to restrict the flow of blood in the blood-transporting layer 1108. The overcoat layer can be prepared by means of a material that is initially in a liquid form or in a form capable of penetrating the interstices of a mesh. This material is preferably a hydrophobic electrically insulating ink. This material is preferably applied by screen printing over a portion of the periphery of the blood-transporting layer (which is preferably in the form of a mesh), thereby surrounding and defining a suitable path for the sample of blood to travel from the point it contacts the blood- transporting layer to the detecting layer 1110. See U. S. Patent No. 5,628,890 for additional discussion concerning how the overcoat layer holds down and fixes the mesh layer in place. The overcoat layer 1123 and the blood-transporting layer 1108 are substantially coplanar. As used herein, the term "coplanar" means that at least one surface of each of two materials resides in the same plane. Substantial coplanar positioning of these layers is preferred because the blood-transporting layer 1108 spreads blood in all directions. In order to limit the spread of blood in undesired areas of the multiple-layer element, the overcoat layer 1123 acts as a barrier to flowing blood. The blood-transporting layer 1108 is adhered to the meter-contactable layer 1114 by means of embedding the edges of the blood- transporting layer 1108 with the overcoat layer 1123. FIG. 28 illustrates the relationship between the planes of the optional overcoat layer 1123 and the blood- transporting layer 1108. As used herein, the expression "substantially coplanar" includes both the situation wherein at least one major surface of the overcoat layer 1123 and at least one major surface of the blood-transporting layer 1108 are in the same plane and the situation wherein at least one major surface of the overcoat layer 1123 extends slightly beyond at least one major surface of the blood- transporting layer 1108. True coplanarity, i. e., the former situation, is difficult to achieve primarily because of manufacturing conditions. Substantial coplanarity, i. e., the latter situation, is more likely to be achieved under actual manufacturing conditions. FIG. 28 illustrates the more likely manufacturing result. However, it is preferred that the overcoat layer 1123 and the blood-transporting layer 1108 approach true coplanarity as much as possible so that the volume of blood needed to be extracted is as small as possible. Method for Preparing the Multiple-Laver Element The multiple-layer element is preferably mass-produced. However, the following method can be used for the manufacture of a single multiple-layer element. The meter-contactable layer 1114 can be provided in the form of a sheet. In a typical construction, the meter-contactable layer 1114 can be a sheet of polyvinyl chloride. The detecting layer 1110 can be screen printed onto the meter- contactable layer 1114 . The detecting layer 1110 can be a biosensor of a type described in U. S. Patent No. 4,545,382, incorporated herein by reference. In a preferred embodiment, the electrodes of the detecting layer 1110 contain a biologically active substance that reacts with glucose, preferably glucose oxidase or glucose dehydrogenase, and an electrically conductive material, preferably carbon, which carries the electrical signal produced by the reaction of glucose with the biologically active substance to an electrical connector in the meter. The generation of the electrical signal may be aided by compounds known as mediators, which increase the electrical signal. See Ferrocene-Mediated Enzyme Electrode for Amperometric Determination of Glucose, Anal. Chem. 1984, 56, 667- 671. The electrical circuit is completed with at least one other electrically conductive material, preferably silver chloride, that is referred to as a reference or counter electrode. The blood-transporting layer 1108 is then placed in a position such that it will be in fluid communication with the detecting layer 1110. The covering layer 1102 can then be adhered to the blood-transporting layer by means of a hot-melt adhesive. Operation Referring now to FIGS. 21 A and 21 B, which illustrate the components of the multiple-layer element in detail, and FIGS. 29A, 29B, 29C, and 29D, which illustrate how the multiple-layer element operates, in order to use the article of this invention for detecting the presence or amount of analyte in a sample of blood, the multiple- layer element 1100 is placed between a lancet stop 1124 and the nosepiece assembly 1126 of the blood collecting apparatus. The nosepiece assembly 1126 comprises a nosepiece 1127 and a seal 1128. The opening 1104 in the covering layer 1102 and the opening 1116 in the meter-contactable layer 1114 are aligned with a lancet 1130 of a lancing assembly 1131. The seal 1128 of the nosepiece assembly 1126 of the blood collecting apparatus is placed against the skin, "S". FIG. 29A illustrates the apparatus prior to application of vacuum. FIG. 29B illustrates the apparatus after application of vacuum, after the skin is stretched and drawn into contact with the covering layer 1102 of the multiple-layer element. The vacuum is applied for a sufficient period of time to cause blood to pool in the skin, which is drawn up into the nosepiece 1127. The lancing assembly is then actuated and the lancet 1130 passes through an opening 1132 in the lancet stop 1124 and the openings in the multiple-layer element (shown in phantom in FIGS. 29A, 29B, 29C, and 29D and designated by reference numerals 1104 and 1116 in FIGS. 21 A and 21 B). Then the lancet penetrates the skin, forming an opening therein. See FIG. 29C. Then the lancet is retracted, thereby forming an unobstructed opening in the skin. The blood, "B", emerges from the unobstructed opening in the skin assisted by vacuum, and contacts the blood-transporting layer 1108, flows along the blood-transporting layer, whereupon it reaches the detecting layer 1110. See FIG. 29D. A chemical reaction occurs at the surface of the detecting layer. The output of the chemical reaction can be read at the electrical contacts 1110a of the detecting layer 1110. After the multiple-layer element is filled, the vacuum is released and the skin comes away from the nosepiece. In the case of an electrochemical sensor, the meter-contactable layer 1114 must physically contact the meter (not shown) in order to have the sensor, i. e., the detecting layer 1110, make electrical contact with the meter, such as by insertion into an electrical connector. The meter-contactable layer can also serve to physically align the multiple-layer element with the meter in order to properly align the lancet with the opening 1116 in the meter-contactable layer. In the case of the reflectance strip, the meter-contactable layer must be mounted in the meter to allow alignment of the light source and the detector of the meter with the reflectance strip, as well as allowing physical alignment of the multiple-layer element with the meter so that the lancet is properly aligned with the opening 11 16 in the meter- contactable layer. While not preferred, it is also possible to provide a workable multiple-layer element that dispenses with the blood-transporting layer. In order to eliminate the blood-transporting layer, the meter-contactable layer and the covering layer can be disposed in such a manner that blood can flow between them to the detecting layer by means of capillary action. In one embodiment involving flow by means of capillary action, the major surface of the meter-contactable layer facing the major surface of the covering layer and the major surface of the covering layer facing the major surface of the meter-contactable layer should be hydrophilic in nature. At least one of the foregoing major surfaces, and preferably both of the foregoing major surfaces, can either be made of a hydrophilic material or can be coated with a hydrophilic material, such as, for example, a surfactant. The hydrophilicity of these layers will cause the blood extracted to flow in the space between the meter- contactable layer and the covering layer to the detecting layer. Thus, it is clear that the blood-transporting layer can be eliminated. In this embodiment, the meter- contactable layer must be of sufficient length so that a capillary channel can be formed between the meter-contactable layer and the covering layer. Thus, if the covering layer is of such a length as to require an opening through which the lancet can pass, it is preferred that the meter-contactable layer also be of such a length as to require an opening through which the lancet can pass. The capillary channel can be, in effect, formed by means of the overcoat layer, which causes a space of capillary width to be formed between the meter-contactable layer and the covering layer. By using the multiple-layer element of this invention, the collection of blood can be carried out in a highly efficient manner. Improving the efficiency of collection will reduce the period of time required to obtain blood for analytical purposes. FIGS. 5-10 and 43-46 illustrate various alternative embodiments of the apparatus of this invention. In FIG. 5, blood extraction device 100 comprises a housing 102. The housing 102 is separable into two portions, a receiving portion 102a and a projecting portion 102b. A gasket 104 is provided to seal the portions 102a and 102b of the housing 102 and to aid in separation of the receiving portion 102a from the projecting portion 102b. The receiving portion 102a forms a tight fit with the projecting portion 102b by means of friction. Projecting elements 102c and 102d are used to guide the projecting portion 102b into the receiving portion 102a. Disposed within the housing 102 are a vacuum pump (not shown), a lancing assembly 108, a battery (not shown), and electronics (not shown). A switch 109 is provided to activate the electronics. The vacuum pump is connected to the lancing assembly 108 by an evacuation tube (not shown). A check valve (not shown) is placed between the vacuum pump and the lancing assembly 108. During the process of obtaining the sample, the receiving portion 102a and the projecting portion 102b are fitted tightly together. The area of the receiving portion 102a of the housing 102 of the device 100 that is to contact the skin is equipped with a seal 110. The seal 110 surrounds an opening 112 in the receiving portion 102a. The opening 112 in the receiving portion 102a allows communication between the surface of the skin and a blood extraction chamber adjacent to a glucose detector 114, shown here in the shape of a strip. When in use, the device 100 is positioned so that the lancing assembly 108 is placed over the region on the surface of the skin from which the sample is to be obtained. In order to obtain the sample of blood, the receiving portion 102a of the housing 102 of the device 100 is placed against the skin, whereby the seal 110 allows a satisfactory vacuum to be effected. The switch 109 is actuated, typically by being pressed, thereby activating the electronics, which starts the vacuum pump. The vacuum pump then provides a suction action. The suction action of the vacuum pump causes the skin circumscribed by the seal 110 to become engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin up to the opening 112. After an appropriate period of time, which is typically pre-set by the programmer of the electronics, the lancing assembly 108 is triggered, thereby causing the lancet 116 to penetrate the skin that has risen up to the opening 112 and that is engorged with blood. The lancet 116 is preferably triggered automatically, by a solenoid valve (not shown) that causes a vacuum-actuated piston (not shown) to trigger the lancet 116. The remaining steps of the process relating to collection of a sample of blood are substantially similar to the steps described in the embodiment shown in FIGS. 1 , 2, 3, and 4. In the embodiment shown in FIG. 5, the glucose detector 114 is inserted into a slot 118 in the projecting portion 102b of the housing 102. The receiving portion 102a of the housing 102 causes the glucose detector 114 to be moved into its proper position for testing. The results obtained from the glucose detector 114 can be displayed on a screen 120, typically a conventional liquid crystal digital display. The receiving portion 102a is separated from the projecting portion 102b when the lancet 116 or glucose detector 114 is being replaced. The receiving portion 102a is fitted tightly to the projecting portion 102b during the process of obtaining a sample of blood. The relative positions of the vacuum pump, the battery, the electronics, the evacuation tube, the check valve, the solenoid valves, and the vacuum-actuated piston are substantially similar to the relative positions of these components as described in the embodiments shown in FIGS. 1 and 2. In FIG. 6, blood extraction device 200 comprises a housing 202. The housing 202 comprises a door portion 202a that is attached to the remaining portion 202b of the housing 202 by a hinge 206. A gasket 207 is provided to seal the housing 202 when the door portion 202a is closed. The door portion 202a can be closed by pivoting it around the hinge 206. When the door portion 202a is closed, the convex portion 202c of the door portion 202a fits precisely into the concave portion 202d of the remaining portion 202b of the housing 202. The remaining edges of the door portion 202a fit tightly against the remaining edges of the remaining portion 202b of the housing 202. Disposed within the housing 202 are a vacuum pump (not shown), a lancing assembly 208, a battery (not shown), and electronics (not shown). A switch (not shown) is provided to activate the electronics . The vacuum pump is connected to the lancing assembly 208 by an evacuation tube (not shown). A check valve (not shown) is placed between the vacuum pump and the lancing assembly 208. During the process of obtaining the sample, the door portion 202a is closed. The area of the door portion 202a of the housing 202 of the device 200 that is to contact the skin is equipped with a seal (not shown). The seal surrounds an opening 212 in the door portion 202a. The opening 212 in the door portion 202a allows communication between the surface of the skin and a blood extraction chamber adjacent to a glucose detector 214, shown here in the shape of a strip. When in use, the device 200 is positioned so that the lancing assembly 208 is placed over the region on the surface of the skin from which the sample is to be obtained. In order to obtain the sample of blood, the door portion 202a of the housing 202 of the device 200 is placed against the skin, whereby the seal allows a satisfactory vacuum to be effected. The switch is actuated, typically by being pressed, thereby activating the electronics, which starts the vacuum pump. The vacuum pump then provides a suction action. The suction action of the vacuum pump causes the skin circumscribed by the seal to become engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin up to the opening 212. After an appropriate period of time, which is typically pre-set by the programmer of the electronics, the lancing assembly 208 is triggered, thereby causing the lancet 216 to penetrate the skin that has risen up to the opening 212 and that is engorged with blood. The lancet 216 is preferably triggered automatically, by a solenoid valve (not shown) that causes a vacuum- actuated piston (not shown) to trigger the lancet 216. The remaining steps of the process relating to collection of a sample of blood are substantially similar to the steps described in the embodiment shown in FIGS. 1 , 2, 3, and 4. In the embodiment shown in FIG. 6, the glucose detector 214 is inserted into slots 218a and 218b of the housing 202. The results obtained from the glucose detector 214 can be displayed on screen 220, typically a conventional liquid crystal digital display. The door portion 202a is opened when the lancet 216 or glucose detector 214 is being replaced. The door portion 202a is closed during the process of obtaining a sample of blood. The relative positions of the vacuum pump, the battery, the electronics, the switch, the evacuation tube, the check valve, the seal, the solenoid valves, and the vacuum-actuated piston are substantially similar to the relative positions of these components as described in the embodiments shown in FIGS. 1 and 2. In FIG. 7, blood extraction device 300 comprises a housing 302. The housing 302 comprises a door portion 302a that is attached to the remaining portion 302b of the housing 302 by a hinge 306. A gasket 307 is provided to seal the housing 302 when the door portion 302a is closed. The door portion 302a can be closed by pivoting it around the hinge 306. When the door portion 302a is closed, the convex portion 302c of the door portion 302a fits precisely into the concave portion 302d of the remaining portion 302b of the housing 302. The remaining edges of the door portion 302a fit tightly against the remaining edges of the remaining portion 302b of the housing 302. Disposed within the housing 302 are a vacuum pump (not shown), a lancing assembly 308, a battery (not shown), and electronics (not shown). A switch (not shown) is provided to activate the electronics. The vacuum pump is connected to the lancing assembly 308 by an evacuation tube (not shown). A check valve (not shown) is placed between the vacuum pump and the lancing assembly 308. During the process of obtaining the sample, the door portion 302a is closed. The area of the door portion 302a of the housing 302 of the device 300 that is to contact the skin is equipped with a seal (not shown). The seal surrounds an opening 312 in the door portion 302a. The opening 312 in the door portion 302a allows communication between the surface of the skin and a blood extraction chamber adjacent to a glucose detector 314, shown here in the shape of a strip. When in use, the device 300 is positioned so that the lancing assembly 308 is placed over the region on the surface of the skin from which the sample is to be obtained. In order to obtain the sample of blood, the door portion 302a of the housing 302 of the device 300 is placed against the skin, whereby the seal allows a satisfactory vacuum to be effected. The switch is actuated, typically by being pressed, thereby activating the electronics, which starts the vacuum pump. The vacuum pump then provides a suction action. The suction action of the vacuum pump causes the skin circumscribed by the seal to become engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin up to the opening 312. After an appropriate period of time, which is typically pre-set by the programmer of the electronics, the lancing assembly 308 is triggered, thereby causing the lancet 316 to penetrate the skin that has risen up to the opening 312 and that is engorged with blood. The lancet 316 is preferably triggered automatically, by a solenoid valve (not shown) that causes a vacuum- actuated piston (not shown) to trigger the lancet 316. The remaining steps of the process relating to collection of a sample of blood are substantially similar to the steps described in the embodiment shown in FIGS. 1 , 2, 3, and 4. In the embodiment shown in FIG. 7, the glucose detector 314 is inserted into a slot 318 of the housing 302. The results obtained from the glucose detector 314 can be displayed on screen 320, typically a conventional liquid crystal digital display. In FIG. 7, connections 322 for the electronics are shown. The door portion 302a is opened when the lancet 316 or glucose detector 314 is being replaced. The door portion 302a is closed during the process of obtaining a sample of blood. The relative positions of the vacuum pump, the battery, the electronics, the switch, the evacuation tube, the check valve, the seal, the solenoid valves, and the vacuum-actuated piston are substantially similar to the relative positions of these components as described in the embodiments shown in FIGS. 1 and 2. In FIG. 8, blood extraction device 400 comprises a housing 402. The housing 402 comprises a door portion 402a that is attached to the remaining portion 402b of the housing 402 by a hinge 406. A gasket 407 is provided to seal the housing 402 when the door portion 402a is closed. The door portion 402a can be closed by pivoting it around the hinge 406. When the door portion 402a is closed, the convex portions 402c and 402d of the door portion 402a fit precisely into the concave portions 402e and 402f, respectively, of the remaining portion 402b of the housing 402. The remaining edges of the door portion 402a fit tightly against the remaining edges of the remaining portion 402b of the housing 402. Disposed within the housing 402 are a vacuum pump (not shown), a lancing assembly 408, a battery (not shown), and electronics (not shown). A switch 409 is provided to activate the electronics. The vacuum pump is connected to the lancing assembly 408 by an evacuation tube (not shown). A check valve (not shown) is placed between the vacuum pump and the lancing assembly 408. During the process of obtaining the sample, the door portion 402a is closed. The area of the door portion 402a of the housing 402 of the device 400 that is to contact the skin is equipped with a seal (not shown). The seal surrounds an opening 412 in the door portion 402a. The opening 412 in the door portion 402a allows communication between the surface of the skin and a blood extraction chamber adjacent to a glucose detector 414, shown here in the shape of a strip. When in use, the device 400 is positioned so that the lancing assembly 408 is placed over the region on the surface of the skin from which the sample is to be obtained. In order to obtain the sample of blood, the door portion 402a of the housing 402 of the device 400 is placed against the skin, whereby the seal allows a satisfactory vacuum to be effected. The switch 409 is actuated, typically by being pressed, thereby activating the electronics, which starts the vacuum pump. The vacuum pump then provides a suction action. The suction action of the vacuum pump causes the skin circumscribed by the seal to become engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin up to the opening 412. After an appropriate period of time, which is typically pre-set by the programmer of the electronics, the lancing assembly 408 is triggered, thereby causing the lancet 416 to penetrate the skin that has risen up to the opening 412 and that is engorged with blood. The lancet 416 is preferably triggered automatically, by a solenoid valve (not shown) that causes a vacuum- actuated piston (not shown) to trigger the lancet 416. The remaining steps of the process relating to collection of a sample of blood are substantially similar to the steps described in the embodiment shown in FIGS. 1 , 2, 3, and 4. In the embodiment shown in FIG. 8, the glucose detector 414 is inserted into a slot 418 of the housing 402. In this embodiment , it is shown that glucose detector 14 can be rotated 90° between two positions to simplify insertion and replacement thereof. The results obtained from the glucose detector 414 can be displayed on screen 420, typically a conventional liquid crystal digital display. The door portion 402a is opened when the lancet 416 or glucose detector 414 is being replaced. The door portion 402a is closed during the process of obtaining a sample of blood. The relative positions of the vacuum pump, the battery, the electronics, the evacuation tube, the check valve, the seal, the solenoid valves, and the vacuum- actuated piston are substantially similar to the relative positions of these components as described in the embodiments shown in FIGS. 1 and 2. In FIG. 9, blood extraction device 500 comprises a housing 502. The housing 502 comprises a cover portion 502a that is attached to the remaining portion 502b of the housing 502 by a hinge 506. A gasket 507 is provided to seal the housing 502 when the cover portion 502a is closed. The cover portion 502a can be closed by pivoting it around the hinge 506. When the cover portion 502a is closed, edges 502c of the cover portion 502a tightly fit against edges 502d of the remaining portion 502b of the housing 502. Disposed within the housing 502 are a vacuum pump (not shown), a lancing assembly 508, a battery (not shown), and electronics (not shown). A switch (not shown) is provided to activate the electronics. The vacuum pump is connected to the lancing assembly 508 by an evacuation tube (not shown). A check valve (not shown) is placed between the vacuum pump and the lancing assembly 508. During the process of obtaining the sample, the cover portion 502a is closed. The cover portion 502a of the housing 502 of the device 500 that is to contact the skin is equipped with a seal 511. The seal 511 surrounds an opening 512 in the cover portion 502a. The opening 512 in the cover portion 502a allows communication between the surface of the skin and a blood extraction chamber adjacent to a glucose detector 514, shown here in the shape of a strip. When in use, the device 500 is positioned so that the lancing assembly 508 is placed over the region on the surface of the skin from which the sample is to be obtained. In order to obtain the sample of blood, the cover portion 502a of the housing 502 of the device 500 is placed against the skin, whereby the seal allows a satisfactory vacuum to be effected. The switch is actuated, typically by being pressed, thereby activating the electronics, which starts the vacuum pump. The vacuum pump then provides a suction action. The suction action of the vacuum pump causes the skin circumscribed by the seal to become engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin up to the opening 512. After an appropriate period of time, which is typically pre-set by the programmer of the electronics, the lancing assembly 508 is triggered, thereby causing the lancet 516 to penetrate the skin that has risen up to the opening 512 and that is engorged with blood. The lancet 516 is preferably triggered automatically, by a solenoid valve (not shown) that causes a vacuum-actuated piston (not shown) to trigger the lancet 516. The remaining steps of the process relating to collection of a sample of blood are substantially similar to the steps described in the embodiment shown in FIGS. 1 , 2, 3, and 4. In the embodiment shown in FIG. 9, the glucose detector 514 is inserted into a slot 518 of the housing 502. The results obtained from the glucose detector 514 can be displayed on screen 520, typically a conventional liquid crystal digital display. The cover portion 502a is opened when the lancet 516 or glucose detector 514 is being replaced. The cover portion 502a is closed during the process of obtaining a sample of blood. The relative positions of the vacuum pump, the battery, the electronics, the switch, the evacuation tube, the check valve, the solenoid valves, and the vacuum- actuated piston are substantially similar to the relative positions of these components as described in the embodiments shown in FIGS. 1 and 2. In FIG. 10, blood extraction device 600 comprises a housing 602. The housing 602 comprises a cover portion 602a that is attached to the remaining portion 602b of the housing 602 by a hinge 606. A gasket 607 is provided to seal the housing 602 when the cover portion 602a is closed. The cover portion 602a can be closed by pivoting it around the hinge 606. When the cover portion 602a is closed, edges 602c of the cover portion 602a tightly fit against edges 602d of the remaining portion 602b of the housing 602. Disposed within the housing 602 are a vacuum pump (not shown), a lancing assembly 608, a battery (not shown), and electronics (not shown). A switch 609 is provided to activate the electronics. The vacuum pump is connected to the lancing assembly 608 by an evacuation tube (not shown). A check valve (not shown) is placed between the vacuum pump and the lancing assembly 608. During the process of obtaining the sample, the cover portion 602a is closed. The cover portion 602a of the housing 602 of the device 600 that contacts the skin is equipped with a seal 611. The seal 611 surrounds an opening 612 in the cover portion 602a. The opening 612 in the cover portion 602a allows communication between the surface of the skin and a blood extraction chamber adjacent to a glucose detector 614, shown here in the shape of a strip. When in use, the device 600 is positioned so that the lancing assembly 608 is placed over the region on the surface of the skin from which the sample is to be obtained. In order to obtain the sample of blood, the cover portion 602a of the housing 602 of the device 600 is placed against the skin, whereby the seal allows a satisfactory vacuum to be effected. The switch is actuated, typically by being pressed, thereby activating the electronics, which starts the vacuum pump. The vacuum pump then provides a suction action. The suction action of the vacuum pump causes the skin circumscribed by the seal to become engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin up to the opening 612. After an appropriate period of time, which is typically pre-set by the programmer of the electronics, the lancing assembly 608 is triggered, thereby causing the lancet 616 to penetrate the skin that has risen up to the opening 612 and that is engorged with blood. The lancet 616 is preferably triggered automatically, by a solenoid valve (not shown) that causes a vacuum-actuated piston (not shown) to trigger the lancet 616. The remaining steps of the process relating to collection of a sample of blood are substantially similar to the steps described in the embodiment shown in FIGS. 1 , 2, 3, and 4. In the embodiment shown in FIG. 10, the glucose detector 614 is inserted into a slot 618 of the housing 602. The results obtained from the glucose detector 614 can be displayed on screen 620, typically a conventional liquid crystal digital display. The cover portion 602a is opened when the lancet 616 or glucose detector 614 is being replaced. The cover portion 602a is closed during the process of obtaining a sample of blood. The relative positions of the vacuum pump, the battery, the electronics, the switch, the evacuation tube, the check valve, the solenoid valves, and the vacuum- actuated piston are substantially similar to the relative positions of these components as described in the embodiments shown in FIGS. 1 and 2. Referring now to FIGS. 43A through 43C, which depict another embodiment of the present invention, blood extraction device 700 comprises a housing 702 having an interior cover portion 702a (shown in the open position in FIG. 43A and in the closed position in FIG. 43B), a door portion 702b (shown in the open position in FIGS. 43A and 43B and in the closed position in FIG. 43C), and a body portion 702c. The interior cover portion 702a advantageously may be positioned, via projection 703, above the body portion 702c by an attachment in the form of hinge 705. Alternatively the interior cover portion 702a may be attached to the body portion 702c by frictional engagement, a detent (not shown), or any combination of a hinge 705, frictional engagement, and a detent. When a hinge 705 is used, it may optionally be spring biased to retain the interior cover portion 702a in the open or closed position. A detent (not shown) may be provided on the interior cover portion 702a to engage with a protrusion (not shown) on the projection 703, or vice versa, to maintain the interior cover portion 702a in the open or closed position when desired. Although a hinge 705 is provided in the embodiment shown in FIGS. 43A through 43C, any other attachment or combination of attachments that allows the interior cover portion 702a to attach to the body portion 702c and alternate between an open and closed position is acceptable. The door portion 702b is attached to the body portion 702c of the housing 702 by a hinge 706. Alternatively, the door portion 702b may be attached to the body portion 702c by frictional engagement, a detent, or any combination of a hinge 706, frictional engagement, and a detent. When a hinge 706 is used, it may optionally be spring biased to retain the door portion 702b in the open or closed position. A detent (not shown) may be provided on the door portion 702b to engage with a protrusion (not shown) on the body portion 702c, or vice versa, to maintain the door portion 702b in the open or closed position when desired. Although a hinge 706 is provided in the embodiment shown in FIGS. 43A through 43C, any other attachment or combination of attachments that allows the door portion 702b to attach to the body portion 702c and alternate between an open and closed position is acceptable. A gasket or other seal arrangement 707 is provided to seal the housing 702 when the interior cover portion 702a and the door portion 702b are closed. Additionally, a latch mechanism (not shown) may be provided to prevent accidental opening of the door portion 702b when the device 700 is in use. Typically, the latch mechanism would provide locking engagement of the door portion 702b with the body portion 702c. Disposed within the housing 702 are a vacuum pump (not shown), a lancet assembly 708 generally comprising a molded plastic piece 730 to which a lancet 716 is affixed, a lancing assembly (not shown) into which the lancet assembly 708 is inserted, a battery (not shown), and electronics (not shown) for purposes described hereinafter. A switch 709 is provided to activate the electronics, which may take the form shown in FIG. 3. The vacuum pump communicates by an evacuation tube (not shown) with the volume enclosed by the door portion 702b when the door portion 702b is in the closed position. Optionally, a check valve (not shown) may be placed in the evacuation tube between the vacuum pump and the volume enclosed by the door portion 702b when the door portion 702b is in the closed position. During the process of obtaining the sample, the interior cover portion 702a and the door portion 702b are closed together with the body portion 702c to form a seal. The seal should be sufficiently tight so that a sufficient vacuum can be obtained by removing air from the volume enclosed by the door portion 702b when the door portion 702b is in the closed position. When the interior cover portion 702a is closed, the lancet 716 is fully enclosed within the interior cover portion 702a, thus preventing the individual being tested from accidentally coming into contact with the lancet 716. The interior cover portion 702a contains an opening 713, FIG. 43B, that allows the lancet 716 to extend therethrough and contact the skin as described hereinafter. The opening 713 may be round, oval, rectangular or any other shape. The interior cover portion 702a may also contain a shoulder portion (not shown) on the interior of the interior cover portion 702a that surrounds all or a portion of the opening 713. When preferably included, the shoulder portion stops the lancet assembly 708 from extending beyond the shoulder portion and prevents the lancet 716 from extending more than is desired into the skin. The preferred lancing depth typically ranges from about 0.5 mm to about 3 mm into the skin. The area of the door portion 702b of the housing 702 that is to contact the skin is equipped with a seal 711 , FIG. 43C. The seal 711 surrounds an opening 712 in the door portion 702b that aligns with the opening 713 in the interior cover portion 702a when both the interior cover portion 702a and the door portion 702b are in the closed position. The opening 712 may be round, oval, rectangular or any other shape. The opening 712 in the door portion 702b allows communication between the surface of the skin and a blood extraction chamber adjacent to a fluid collector, shown here in the form of a glucose detector 714, FIG. 43B, which may take the shape of a strip. Other types of fluid collectors may also be used, and those of skill in the art will recognize that the present embodiment could easily be modified to include more than one fluid collector. Preferably, the glucose detector 714 used in the embodiment shown in FIGS. 43A through 43C contains a opening 715 in approximately the middle of glucose detector 714 for the lancet 716 to pass through. The opening 715 is preferably in alignment with openings 712 and 713 and the lancet 716. The opening 715 may be covered with a mesh. When in use, the device 700 is positioned so that the lancing assembly is placed over the region on the surface of the skin from which the fluid sample is to be obtained such that the lancing assembly is approximately perpendicular to the surface of the skin. In order to obtain the sample of blood, the door portion 702b of the housing 702 is placed against the skin, whereby the seal 711 surrounding opening 712 allows a satisfactory vacuum to be effected. The switch 709 is actuated, typically by being pressed, thereby activating the electronics, described in FIG. 3 and discussed above, which starts the vacuum pump. The action of the vacuum pump withdraws air from the volume enclosed by the door portion 702b when the door position 702b is in the closed position and causes the skin circumscribed by the seal 711 to be drawn toward the opening 712. This results in the skin becoming engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin to the opening 712 in the door portion 702b. After an appropriate period of time, which is typically pre-set by the programmed electronics, the lancing assembly is triggered, thereby causing the lancet 716 to penetrate the skin that has been pulled up into the opening 712 of the door portion 702b. The lancet 716 is preferably triggered automatically by activation of a solenoid valve (not shown) that causes a vacuum-actuated piston (not shown) to trigger the lancet 716. The remaining steps of the process relating to collection of a sample of blood are substantially similar to the steps described when using the embodiment shown in FIGS. 1 through 4. In the embodiment shown in FIGS. 43A through 43C, the glucose detector 714 is inserted into a slot 718 of the projection 703 of the housing 702. Glucose detector 714 contains one or more electrical contacts (not shown) on the end inserted into the slot 718 which engage one or more electrical contacts (not shown) positioned within the slot 718. In the embodiment shown in FIGS. 43A through 43C, the slot 718 may be designed in such a manner that the glucose detector 714 is placed into the slot 718 at an angle that advantageously allows for easier and cleaner removal of the glucose detector 714 at the conclusion of the test. Alternatively, the slot 718 may be designed in such a manner that the glucose detector 714 is placed into the slot 718 substantially parallel to the upper surface of the interior cover portion 702a when the interior cover portion 702a is in the closed position. Alignment channels 719a and 719b on either side of the exterior of the interior cover portion 702a may be provided to align the glucose detector 714 so that the glucose detector 714 is properly aligned with the lancet 716. Alignment features (not shown) within the interior of the door portion 702b may also be provided to assist in the alignment of the glucose detector 714 over the lancet 716 when the door portion 702b is closed. Both the interior cover portion 702a and the door portion 702b are closed during the process of obtaining a sample of blood. After the lancet 716 pierces the skin and is retracted, blood is withdrawn, under the aid of the vacuum, toward and onto the glucose detector 714. When a sufficient amount of blood has been collected, the glucose detector 714 generates a signal which results in deactivation of the vacuum pump and the vacuum is released by, for example, an electronically controlled valve. Alternatively, the vacuum pump may be stopped after a pre-set time interval. The blood collection device 700 may then be removed from the individual's skin. Thereafter, the glucose detector 714 generates a signal, as described above, indicative of glucose level, which signal is transmitted via electrical circuitry to the electronics housed in the blood collection device 700. The signal is processed by such electronics, in the manner described above, and the results obtained from the glucose detector 714 can be displayed on a screen 720, typically a conventional liquid crystal digital display. Other manners of display may also be used. Upon completion of the measurement, the door portion 702b may be opened and the glucose detector 714 may be replaced. When it is desired to replace the lancet 716, both the door portion 702b and the interior cover 702a are opened, as described above. The lancet 716 and the glucose detector 714 may be replaced immediately after use, immediately before use, or may be replaced at any other time. Referring now to FIGS. 44A and 44B, which depict another embodiment of the present invention, blood extraction device 800 comprises a housing 802. The housing 802 includes a door portion 802a (shown in the open position in FIG. 44A and in the closed position in FIG. 44B) that is attached to the body portion 802b of the housing 802 by an attachment in the form of a hinge 806. Alternatively, the door portion 802a may be attached to the body portion 802b by frictional engagement, a detent (not shown), or any combination of a hinge 806, frictional engagement, and a detent. When a hinge 806 is used, it may optionally be spring biased to retain the door portion 802a in the open or closed position. A detent (not shown) may be provided on the door portion 802a to engage with a protrusion (not shown) on the body portion 802b, or vice versa, to maintain the door portion 802a in the open or closed position when desired. Although a hinge 806 is provided in the embodiment shown in FIGS. 44A and 44B, any other attachment or combination of attachments that allows the door portion 802a to attach to the body portion 802b and alternate between open and closed positions is acceptable. The hinge 806 may be located on the body portion 802b as shown in FIGS. 44A and 44B or may alternatively be located on one side of the body portion 802b. A gasket or other seal arrangement 807 is provided to seal the housing 802 when the door portion 802a is closed. Additionally, a latch mechanism may be included to prevent accidental opening of the door portion 802a when the blood collection device 800 is in use. Typically, the latch mechanism would provide locking engagement of the door portion 802a with the body portion 802b. Disposed within the housing 802 are a vacuum pump (not shown), a lancet assembly 808 generally comprising a molded plastic piece 830 to which a lancet 816 is affixed, a lancing assembly (not shown) into which the lancet assembly 808 is inserted, a battery (not shown), and electronics (not shown). A switch 809, FIG. 44B, is provided to activate the electronics, which may take the form as shown in FIG. 3. The vacuum pump communicates by an evacuation tube (not shown) with the volume enclosed by the door portion 802a when the door portion 802a is in the closed position. Optionally a check valve (not shown) may be placed in the evacuation tube between the vacuum pump and the volume enclosed by the door portion 802a when the door portion 802a is in the closed position. During the process of obtaining the sample, the door portion 802a is closed to form a seal. The seal should be sufficiently tight so that a sufficient vacuum can be obtained by removing air from the volume enclosed by the door portion 802a when the door portion 802a is in the closed position. The area of the door portion 802a of the housing 802 that is to contact the skin is equipped with a seal (not shown). The seal surrounds an opening 812 (shown in dotted lines in FIG. 44B) in the door portion 802a. The opening 812 may be round, oval, rectangular or any other shape. The opening 812 in the door portion 802a allows communication between the surface of the skin and a blood extraction chamber adjacent to a fluid collector, shown here in the form of a glucose detector 814, which may take the shape of a strip. Other types of fluid collectors may also be used, and those of skill in the art will recognize that the present embodiment could easily be modified to include more than one fluid collector. Preferably, the glucose detector 814 used in the embodiment shown in FIGS. 44A and 44B contains an opening 815 in approximately the middle of glucose detector 814 for the lancet 816 to pass through. The opening 815 is preferably in alignment with opening 812 and the lancet 816. The opening 815 may be covered with a mesh. When in use, the blood collection device 800 is positioned so that the lancing assembly is placed over the region on the surface of the skin from which the fluid sample is to be obtained such that the lancing assembly is approximately perpendicular to the surface of the skin. In order to obtain the sample of blood, the door portion 802a of the housing 802 is placed against the skin, whereby the seal surrounding opening 812 allows a satisfactory vacuum to be effected. The switch 809 is actuated, typically by being pressed, thereby activating the electronics, described in FIG. 3 and discussed above, which starts the vacuum pump. The vacuum pump then provides a suction action. The action of the vacuum pump withdraws air from the volume enclosed by the door portion 802a when the door portion 802a is in the closed position, and causes the skin circumscribed by the seal to be drawn toward the opening 812. This results in the skin becoming engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin to the opening 812 in the door portion 802a. After an appropriate period of time, which is typically pre-set by the programmed electronics, the lancing assembly is triggered, thereby causing the lancet 816 to penetrate the skin that has been pulled up into the opening 812 of the door portion 802a and that is engorged with blood. The lancet 816 is preferably triggered automatically by activation of a solenoid valve (not shown) that causes a vacuum-actuated piston (not shown) to trigger the lancet 816. The remaining steps of the process relating to collection of a sample of blood are substantially similar to the steps described when using the embodiment shown in FIGS. 1 through 4. In the embodiment shown in FIGS. 44A and 44B, the glucose detector 814 is inserted into slot 818 of the door portion 802a of the housing 802. Alignment channels 819a and 819b, preferably C-shaped, along either side of slot 818 can be used to align the glucose detector 814 so that the glucose detector 814 is properly aligned with the lancet 816. Preferably, the alignment channels 819a and 819b cover only a small portion of each side of glucose detector 814 to minimize the chance of blood being left in the slot 818 and alignment channels 819a and 819b when the glucose detector 814 is removed. In a preferred embodiment, some portion of the glucose detector 814 should extend beyond the top of the door portion 802a to ensure easy removal of the glucose detector 814. In the embodiment shown in FIGS. 44A and 44B, glucose detector 814 contains one or more electrical contacts (not shown) on the end opposite the end inserted into slot 818 that engage one or more electrical contacts (not shown) positioned within a slot 821 on the body portion 802b. The end of the glucose detector 814 with the electrical contacts is inserted into slot 821 on the body portion 802b by the movement of the door portion 802a when the door portion 802a is closed. Alternatively, the blood extraction device 800 may be designed in such a way that the end of the glucose detector 814 containing one or more electrical contacts is inserted into slot 818 to engage with one or more electrical contacts positioned within slot 818 and the end of the glucose detector 814 opposite the end containing the electrical contacts is inserted into slot 821 by the movement of the door portion 802a when the door portion 802a is closed. Alignment channels 819a and 819b preferably may also stop the lancet assembly 808 from extending beyond the alignment channels 819a and 819b and prevent the lancet 816 from extending more than is desired into the skin. The preferred lancing depth typically ranges from about 0.5 mm to about 3 mm into the skin. The door portion 802a is closed during the process of obtaining a sample of blood. After the lancet 816 pierces the skin and is retracted, blood is withdrawn, under the aid of the vacuum, toward and onto the glucose detector 814. When a sufficient amount of blood has been collected, the glucose detector 814 generates a signal that results in deactivation of the vacuum pump and the vacuum is released by, for example, an electronically controlled valve. Alternatively, the vacuum pump may be stopped after a pre-set time interval. The blood collection device 800 may then be removed from the individual's skin. Thereafter the glucose detector 814 generates a signal, as described above, indicative of glucose level, which signal is transmitted via electrical circuitry to the electronics housed in the blood collection device 800. The signal is processed by such electronics, in the manner described above, and the results obtained from the glucose detector 814 can be displayed on a screen 820, typically a conventional liquid crystal digital display. Other manners of display may also be used. Upon completion of the measurement, the door portion 802a may be opened and the glucose detector 814 and the lancet 816 may be replaced. The lancet 816 and the glucose detector 814 may be replaced immediately after use, immediately before use or may be replaced at any other time. Referring now to FIGS. 45A through 45E, which depict another embodiment of the present invention, blood extraction device 900 comprises a housing 902 having a door portion 902a (shown in the open position in FIG. 45A, in a partially closed position in FIG. 45B, and in the closed position in FIGS. 45C through 45E) that is attached to the body portion 902b of the housing 902 by an attachment in the form of a hinge 906. Alternatively, the door portion 902a may be attached to the body portion 902b by frictional engagement, a detent (not shown) or any combination of a hinge 906, frictional engagement, and a detent. When a hinge 906 is used, it may optionally be spring biased to retain the door portion 902a in the open or a closed position. A detent (not shown) may be provided on the door portion 902a to engage with a protrusion (not shown) on the body portion 902b, or vice versa, to maintain the door portion 902a in the open or closed position when desired. Although a hinge 906 is provided in the embodiment shown in FIGS. 45A through 45E, any other attachment or combination of attachments that allows the door portion 902a to attach to the body portion 902b and alternate between an open and closed position is acceptable. A gasket or other seal arrangement (not shown) is provided to seal the housing 902 when the door portion 902a is closed. Additionally, a latch mechanism may be included to prevent accidental opening of the door portion 902a when the blood collection device 900 is in use. Typically, the latch mechanism would provide locking engagement of the door portion 902a with the body portion 902b. Disposed within the housing 902 are a vacuum pump (not shown), a lancet assembly 908 generally comprising a molded plastic piece 930 to which a lancet 916 is affixed, a lancing assembly (not shown) into which the lancet assembly 908 is inserted, a battery (not shown), and electronics (not shown) for purposes described hereinafter. A switch 909 is provided to activate the electronics, which may take the form as shown in FIG. 3. The vacuum pump communicates by an evacuation tube (not shown) with the volume enclosed by the door portion 902a when the door portion 902a is in the closed position. Optionally a check valve (not shown) may be placed in the evacuation tube between the vacuum pump and the volume enclosed by the door portion 902a when the door portion 902a is in the closed position. During the process of obtaining the sample, the door portion 902a is closed to form a seal. The seal should be sufficiently tight so that a sufficient vacuum can be obtained by removing air from the volume enclosed by the door portion 902a when the door portion 902a is in the closed position. The area of the door portion 902a of the housing 902 that is to contact the skin is equipped with a seal 910, FIG. 45B. The seal 910 surrounds an opening 912 in the door portion 902a. The opening 912 may be round, oval, rectangular or any other shape. The opening 912 in the door portion 902a allows communication between the surface of the skin and a blood extraction chamber adjacent to a fluid collector, shown here in the form of a glucose detector 914, which may take the shape of a strip. Other types of fluid collectors may also be used, and those of skill in the art will recognize that the present embodiment could easily be modified to include more than one fluid collector. Preferably, the glucose detector 914 used in the embodiment shown in FIGS. 45A through 45E contains a semi-circular notch (not shown) in the region of the glucose detector 914 that comes into contact with the blood. The semi-circular notch may be covered with mesh. When in use, the blood collection device 900 is positioned so that the lancing assembly is placed over the region on the surface of the skin 924, FIG. 45C, from which the fluid sample is to be obtained such that the lancing assembly is approximately perpendicular to the surface of the skin 924. In order to obtain the sample of blood, the door portion 902a of the housing 902 is placed against the skin 924, whereby the seal 910 surrounding opening 912 allows a satisfactory vacuum to be effected. The switch 909 is actuated, typically by being pressed, thereby activating the electronics, described in FIG. 3 and discussed above, which starts the vacuum pump. The action of the vacuum pump withdraws air from the volume enclosed by the door portion 902a when the door portion 902a is in the closed position and causes the skin circumscribed by the seal 910 to be drawn toward the opening 912. This results in the skin becoming engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin to the opening 912 in the door portion 902a, as depicted in FIGS. 45C through 45E. After an appropriate period of time, which is typically pre-set by the programmed electronics, the lancing assembly is triggered, thereby causing the lancet 916 to penetrate the skin that has been pulled up into the opening 912 of the door portion 902a. The lancet 916 is preferably triggered automatically by activation of a solenoid valve (not shown) that causes a vacuum-actuated piston (not shown) to trigger the lancet 916. In the embodiment shown in FIGS. 45A through 45E, the glucose detector 914 is inserted into a slot (not shown) of a movable projection 903 of the body portion 902b of the housing 902. Glucose detector 914 contains one or more electrical contacts (not shown) on the end inserted into the slot which engage one or more electrical contacts (not shown) positioned within the slot. After the glucose detector 914 is positioned within the slot of the movable projection 903, movable projection 903 is pushed inwardly. A latch or other mechanism holds the movable projection 903 in the inward position until triggered, as discussed below. As shown in FIGS. 45B through 45C, when the door portion 902a is closed, a cam surface 926 on the interior of the door portion 902a moves the movable projection 903 and the glucose detector 914 in a direction towards the lancing assembly and lancet assembly 908. Although a cam surface 926 is shown in FIG. 45A, other alignment approaches may also be utilized. The lancet 916 is then triggered, penetrates the skin 924, as shown in FIG. 45D, and is quickly retracted. Shortly after the lancet 916 is triggered, as discussed above, the movable projection 903 is triggered, preferably electronically such as by the release of a latch or other mechanism, causing an interior portion 903a of the movable projection 903 to move outwardly, such as by a sliding mechanism, and thereby causing the glucose detector 914 to move to a position near the position where the lancet contacted the skin 924, as shown in FIG. 45E, causing the glucose detector 914 to come into contact with the blood. The area of the interior of the door portion 902a immediately adjacent to the opening 912 may also preferably stop the lancet assembly 908 from extending beyond the door portion 902a and prevents the lancet 916 from extending more than is desired into the skin. The preferred lancing depth typically ranges from about 0.5 mm to about 3 mm into the skin. The door portion 902a is closed during the process of obtaining a sample of blood. After the lancet 916 pierces the skin 924 and is retracted, blood is withdrawn, under the aid of the vacuum, toward and onto the glucose detector 914. When a sufficient amount of blood has been collected, the glucose detector 914 generates a signal which results in deactivation of the vacuum pump and the vacuum is released by, for example, an electronically controlled valve. Alternatively, the vacuum pump may be stopped after a pre-set time interval. The blood collection device 900 may then be removed from the individual's skin. Thereafter, the glucose detector 914 generates a signal, as described above, indicative of glucose level, which signal is transmitted via electrical circuitry to the electronics housed in the blood collection device 900. The signal is processed by such electronics, in the manner described above, and the results obtained from the glucose detector 914 can be displayed on a screen 920, typically a conventional liquid crystal digital display. Other manners of display may also be used. Upon completion of the measurement, the door portion 902a may be opened and the glucose detector 914 and the lancet 916 may be replaced. The lancet 916 and the glucose detector 914 may be replaced immediately after use, immediately before use or may be replaced at any other time. Referring now to FIGS. 46A through 46C, which depict another embodiment of the present invention, blood extraction device 1000 comprises a housing 1002 having a door portion 1002a (shown in the closed position in FIGS. 46A through 46C) that is attached to the body portion 1002b of the housing 1002 by an attachment in the form of a hinge (not shown). Alternatively, the door portion 1002a may be attached to the body portion 1002b by frictional engagement, a detent (not shown), or any combination of a hinge, frictional engagement, and a detent. When a hinge is used, it may optionally be spring biased to retain the door portion 1002a in the open or closed position. A detent (not shown) may be provided on the door portion 1002a to engage with a protrusion (not shown) on the body portion 1002b, or vice versa, to maintain the door portion 1002a in the open or closed position when desired. Although a hinge (not shown) is provided in the embodiment shown in FIGS. 46A through 46C, any other attachment or combination of attachments that allows the door portion 1002a to attach to the body portion 1002b and alternate between an open and closed position is acceptable. A gasket or other seal arrangement 1007 is provided to seal the housing 1002 when the door portion 1002a is closed. Alternatively, the housing 1002 may also include a movable interior cover portion (not shown), similar to that described in the embodiment shown in FIGS. 43A through 43C, that advantageously may be positioned around the lancing assembly (not shown) in a manner to allow the movable interior cover portion to be opened and closed. Any attachment that allows the movable interior cover portion to attach to the body portion 1002b and alternate between an open and closed position is acceptable. Additionally, a latch mechanism may be included to prevent accidental opening of the door portion 1002a when the blood collection device 1000 is in use. Typically, the latch mechanism would provide locking engagement of the door portion 1002a with the body portion 1002b. Disposed within the housing 1002 are a vacuum pump (not shown), a lancet assembly 1008 generally comprising a molded plastic piece 1030 to which a lancet 1016 is affixed, a lancing assembly (not shown) into which the lancet assembly 1008 is inserted, a battery (not shown), and electronics (not shown) for purposes described hereinafter. A switch 1009 is provided to activate the electronics, which may take the form as shown in FIG. 3. The vacuum pump communicates by an evacuation tube (not shown) with the volume enclosed by the door portion 1002a when the door portion 1002a is in the closed position. Optionally a check valve (not shown) may be placed in the evacuation tube between the vacuum pump and the volume enclosed by the door portion 1002a when the door portion 1002a is in the closed position. During the process of obtaining the sample, the door portion 1002a is closed to form a seal. The seal should be sufficiently tight so that a sufficient vacuum can be obtained by removing air from the volume enclosed by the door portion 1002a when the door portion 1002a is in the closed position. The area of the door portion 1002a of the housing 1002 that is to contact the skin is equipped with a seal 1010. The seal 1010 surrounds an opening 1012 in the door portion 1002a. The opening 1012 may be round, oval, rectangular or any other shape. The opening 1012 in the door portion 1002a allows communication between the surface of the skin and a blood extraction chamber adjacent to a fluid collector, shown here in the form of a glucose detector 1014, which may take the shape of a strip. Other types of fluid collectors may also be used, and those of skill in the art will recognize that the present embodiment could easily be modified to include more than one fluid collector. Preferably, the glucose detector 1014 contains at least one opening (not shown) in approximately the middle of glucose detector 1014 for the lancet 1016 to pass through. In this embodiment, at least one opening in approximately the middle of glucose detector 1014 is preferably in alignment with opening 1012 and lancet 1016 and may be covered with a mesh. Alternatively, the glucose detector 1014 used in the embodiment shown in FIGS. 46A through 46C may contain a semi-circular notch (not shown) in the region of the glucose detector 1014 that comes into contact with the blood. The semi-circular notch may be covered with a mesh. When in use, the blood collection device 1000 is positioned so that the lancing assembly is placed over the region on the surface of the skin from which the fluid sample is to be obtained such that the lancing assembly is approximately perpendicular to the surface of the skin. In order to obtain the sample of blood, the door portion 1002a of the housing 1002 is placed against the skin, whereby the seal 1010 surrounding opening 1012 allows a satisfactory vacuum to be effected. The switch 1009 is actuated, typically by being pressed, thereby activating the electronics, described in FIG. 3 and discussed above, which starts the vacuum pump. The action of the vacuum pump withdraws air from the volume enclosed by the door portion 1002a when the door portion 1002a is in the closed position and causes the skin circumscribed by the seal 1010 to be drawn toward the opening 1012. This results in the skin becoming engorged with blood. Engorgement of the skin with blood is accompanied by a stretching of and rising up of the skin to the opening 1012 in the door portion 1002a. After an appropriate period of time, which is typically pre-set by the programmed electronics, the lancing assembly is triggered, thereby causing the lancet 1016 to penetrate the skin that has been pulled up into the opening 1012 of the door portion 1002a. The lancet 1016 is preferably triggered automatically by activation of a solenoid valve (not shown) that causes a vacuum-actuated piston (not shown) to trigger the lancet 1016. In the embodiment shown in FIGS. 46A through 46C, the glucose detector 1014 is inserted into a slot 1018 of a movable projection 1003 of the body portion 1002b of the housing 1002. Glucose detector 1014 contains one or more electrical contacts (not shown) on the end inserted into the slot 1018 which engage one or more electrical contacts (not shown) positioned within the slot 1018. Preferably, after the glucose detector 1014 is positioned within the slot 1018 of movable projection 1003, movable projection 1003 is pushed in a retract manner. A latch or other mechanism holds the projection in the retracted position until triggered, as discussed below. To obtain a sample of blood, the door portion 1002a is closed. As discussed above, a vacuum is created and the skin becomes engorged with blood. After an appropriate period of time, the lancet 1016 is then triggered and, depending on the type of glucose detector 1014 being used, the lancet 1016 contacts the skin by moving through an opening in approximately the middle of glucose detector 1014 or moving beyond the end of the glucose detector 1014 containing a semi-circular notch. The lancet 1016 then penetrates the skin, and is quickly retracted. Shortly after the lancet 1016 is triggered and retracted, as discussed above, the movable projection 1003 is triggered, causing the glucose detector 1014 to extend laterally across the width of the blood collection device 1000, as shown by the arrow in FIG. 46A, in order to come into contact with the blood. This movement may be caused by the release of a latch. Alternatively, the glucose detector 1014 may be moved incrementally through the action of a solenoid or other electromechanical device. In one embodiment, the glucose detector 1014 may be moved via a pivoting projection 1003a, FIG. 46B. In another embodiment, the glucose detector 1014 may be moved via a four-bar linkage 1004, FIG. 46C. The movable projection 1003 may also comprise an extension 1025 that extends laterally across the width of the blood collection device 1000. When present, extension 1025 stops the lancet assembly 1008 from extending beyond the extension 1025 and prevents the lancet 1016 from extending more than is desired into the skin. The preferred lancing depth typically ranges from about 0.5 mm to about 3 mm into the skin. After the lancet 1016 pierces the skin and is retracted, the movable projection 1003 is triggered and the glucose detector 1014 is moved, as discussed above, so that a wicking portion (not shown) of glucose detector 1014 is above the opening created in the skin. Blood is then withdrawn, under the aid of the vacuum, toward and onto the detector 1014. When a sufficient amount of blood has been collected, the glucose detector 1014 then generates a signal which results in deactivation of the vacuum pump and the vacuum is released by, for example, an electronically controlled valve. Alternatively, the vacuum pump may be stopped after a pre-set time interval. The blood collection device 1000 may then be removed from the individual's skin. Thereafter, the glucose detector 1014 generates a signal, as described above, indicative of glucose level, which signal is transmitted via electrical circuitry to the electronics housed in the blood collection device 1000. The signal is processed by such electronics, in the manner described above, and the results obtained from the glucose detector 1014 can be displayed on a screen 1020, typically a conventional liquid crystal digital display. Other manners of display may also be used. Upon completion of the measurement, the door portion 1002a may be opened and the glucose detector 1014 and the lancet 1016 may be replaced. The lancet 1016 and the glucose detector 1014 may be replaced immediately after use, immediately before use or may be replaced at any other time. In each of the embodiments shown in the foregoing FIGS. 5-10 and 43-46, the housing, vacuum pump, lancing assembly, lancet assembly, battery, electronics, evacuation tube, check valve, nosepiece assembly, blood extraction chamber, lancet, and solenoid valve can be made of the same materials as the corresponding components of the apparatus shown in FIGS. 1 , 2, and 3. The seals 104, 207, 307, 407, 507, 607, 707, 807, 907, and 1007 can be made of the same material as the seal of the nosepiece assembly. The components shown in the foregoing FIGS. 5-10 and 43-46 function in the same manner as do the corresponding components of the apparatus shown in FIGS. 1 , 2, and 3. FIG. 20 illustrates a preferred installation of the lancing assembly shown in FIGS. 11 and 12 inside a prototype of an embodiment of the blood collecting apparatus of this invention. The lancing assembly 1200, shown in its retracted pre- thrust position, has been fitted with a standard lancet assembly 1202 and a three- way solenoid valve 1204. The cap 1206 of the lancing assembly 1200 is fitted into the partition 1207 of the apparatus 1000, thereby forming an effective seal against the partition 1207. The apparatus 1000 comprises a housing 1002, which comprises a door portion 1002a and a body portion 1002b. The exit port 1208 of the lancing assembly 1200 is connected to a vacuum pump 1210 by means of a passageway 1212, such as, for example, a connecting tube. The passageway 1212 is also connected to a cavity 1213 inside the door portion 1002a of the apparatus 1000. In this manner, the vacuum pump 1210 can deliver an equal level of vacuum pressure to the cavity 1213 and to the exit port 1208. The vacuum pressure inside the cavity 1213 can be maintained at a level at which the apparatus 1000 operates, because the vacuum pump 1210 can draw evacuated air from the cavity 1213 at a rate faster than the rate at which ambient air leaks into the cavity 1213 by way of the door seal 1007, the seal placed against the skin of a patient 1010, and the seal formed between the cap 1206 and the partition 1207 (not shown). The body 1002b of the housing 1002 of the apparatus 1000 contains air having a pressure level equal to the ambient pressure surrounding the apparatus. The level of pressure inside the body 1002b of the housing 1002 does not change during operation of the apparatus because the body 1002b of the housing 1002 contains a sufficient number of openings (not shown) that communicate with the surrounding ambient air. The air inside the body 1002b of the housing 1002 can enter the lancing assembly 1200 through the inlet port 1214 when the solenoid valve 1204 is activated to begin the lancing step. The difference in air pressure between the ambient air inside the body 1002b of the housing 1002 and the evacuated air inside the cavity 1213 in the door portion 1002a of the housing 1002 brings about the differential gas pressure needed to operate the lancing assembly. During the lancing step, the thrusting motion of the lancet assembly 1202 is halted by a lancet stop 1216. The lancet stop 1216 has an opening (not shown) that allows the lancet 1218 to pass through and penetrate the skin which is placed against the seal 1010. The lancing assembly in FIG. 20 can thus be used in a manner substantially identical to that shown in FIGS. 15A, 15B, and 15C. It should be noted that the designs of the various housings shown in FIGS. 5-14 can be modified without substantially affecting the functioning of the components disposed within the housing or on the surface of the housing. For example, the shapes of the housings, the shapes of the door portions of the housings, the shapes of the cover portions of the housings, and the shapes of the remaining portions of the housings can be modified without departing from the scope and spirit of this invention. This invention provides numerous advantages over blood extraction devices of the prior art. Among these advantages are the following: 1. Ability to use parts of the body, other than the finger, as a site for the extraction of blood; 2. Reduction of pain by eliminating the need to lance the finger; 3. Increase in speed of collection of blood samples by means of pre- treatment comprising a combination of stretching of the skin in conjunction with heat or vacuum or both heat and vacuum; 4. Incorporation of glucose detector in apparatus for extracting the blood sample. The following examples illustrate various features of the present invention but are not intended to in any way limit the scope of the invention as set forth in the claims. In the following examples, the term "pierce" and forms thereof and the term "puncture"" and forms thereof are used interchangeably. Although the term "glucose detector" is used herein, one of ordinary skill in the art will recognize that the apparatus and methods of the present invention may also be used to perform other diagnostic tests. EXAMPLES Example 1 This example illustrates that greater volumes of blood can be extracted and collected by applying a vacuum, pulsed or continuous, after piercing than can be extracted and collected when no vacuum is applied. No vacuum was applied prior to piercing. Each of four people had his forearm (dorsal forearm) punctured four times (at four different positions on the forearm) with a "BD ULTRA-FINE" lancet in a "MEDISENSE" lancet assembly (Model no. 97101) at two different levels of vacuum (-2.5 psig and -5.0 psig) and for each different vacuum pulsing frequencies (0, 0.2, 0.8, 3.2, 12.8, 25, 100 hertz). The vacuum was applied with a pipette tip having a diameter of 8 mm ("RAIN IN RT-200"). Four control runs without a vacuum were also carried out (one puncture per person). A total of 60 punctures per person were carried out. Accordingly, it can be seen that a total of 240 runs were carried out. The vacuum was applied for a duration of 30 seconds after puncturing. Blood was collected into capillary tubes. In the control runs, the samples were extracted and collected 30 seconds after puncturing. The amount of blood collected was determined by measuring the length of blood in the tubes. The percentage of collections in which the volume of blood collected exceeded 1.0 μL was calculated. Sensation of pain was also recorded. The following pain scores were used: Pain of 1 = person did not feel anything or not sure if anything was felt Pain of 2 = person felt definite prick, not as painful as piercing of finger by standard finger lancet Pain of 3 = person felt definite pain, approximately equal to a piercing of finger by standard finger lancet Blood collection results are set forth in TABLE I. TABLE I With no vacuum, average volume of blood collected was 0.8 μL and 31 % of the samples collected contained more than 1 μL. The pain results were as follows: pain of 1 = 81 % pain of 2 = 17% pain of 3 = 2% The control runs (no vacuum) provided much lower volumes of blood collected than did the runs where vacuum was applied. Increased vacuum resulted in higher volumes of blood extracted. The pain was minimal, with only 2% of the punctures resulting in pain comparable to that resulting from a piercing of the finger. Example 2 This example illustrates that application of vacuum prior to piercing as well as after piercing results in a greater volume of blood extracted than does the application of vacuum only after piercing. Each of four people had his forearm (dorsal forearm, middle of forearm) punctured sixteen times (at sixteen different positions on the forearm) with a "BD ULTRA-FINE" lancet in a modified "MEDISENSE" lancet assembly at four different levels of vacuum. The four levels of vacuum used were -2.5, -5.0, -7.5, and -10.0 psig. The "MEDISENSE" lancet device was modified to allow vacuum to be pulled through the lancet assembly. Four punctures per person were carried out at each of the four levels of continuous vacuum. Accordingly, it can be seen that a total of 64 runs were carried out. Prior to puncturing, the vacuum was applied for a period of 30 seconds; subsequent to puncturing, the vacuum was applied for a period of 30 seconds. The skin was under vacuum at the time the lancet was triggered. After the lancet was triggered, the lancet assembly was removed, and the vacuum was used to apply the same level of vacuum that had been used for the vacuum prior to puncturing. The vacuum, both prior to puncturing and subsequent to puncturing, was applied with a pipette tip having a diameter of 8 mm ("RAININ RT-200"). The pipette tip of the vacuum device was held level to the plane of the skin. Blood was then collected into capillary tubes. The amount of blood collected was determined by measuring the length of blood in the tubes. The percentage of collections in which the volume of blood collected exceeded 1.0 μL was calculated. Sensation of pain was also recorded. Blood collection results are set forth in TABLE II. TABLE The pain results were as follows: pain of 1 = 58% pain of 2 = 31 % pain of 3 = 11 % A nearly linear relationship between level of vacuum and volume of blood collected was observed. The average volume of blood collected with vacuum applied prior and after piercing was approximately twice that collected with vacuum applied only after piercing without vacuum applied prior to piercing. See the results of Example 1 for this comparison (7.8 μL vs. 3.1 μL). The volume of blood collected was always above 1 μL for all levels of vacuum, except -2.5 psig. Example 3 This example illustrates that localized heating of the area to be pierced followed by vacuum after piercing results in a greater volume of blood being extracted than does extraction with only vacuum after piercing. Each of four people had his forearm (dorsal forearm, middle of forearm) punctured eight times (at eight different positions on the forearm) with a "BD ULTRA-FINE" lancet in a "MEDISENSE" lancet assembly with heat applied (45 °C) prior to piercing for two different time periods, 15 seconds and 60 seconds. A total of 32 runs were carried out, 16 runs where the pre-heating duration was 15 seconds and 16 runs where the pre-heating duration was 60 seconds. Heat was applied with a heating block, which was an aluminum block having a square face covered with a "KAPTON" film heater element controlled by an "OMEGA" DP41 temperature controller using a T-type thermocouple. Vacuum was applied after each puncturing for 30 seconds at -5.0 psig. Blood was collected into capillary tubes. The amount of blood collected was determined by measuring the length of blood in the tubes. The percentage of collections in which the volume of blood collected exceeded 1.0 μL was calculated. Pain was also tracked. Blood collection results are set forth in TABLE III. TABLE The pain results were as follows: pain of 1 = 91% pain of 2 = 9% pain of 3 = 0% The average volume of blood collected using a pre-heating duration of 15 seconds was more than twice the average volume of blood collected at a post-puncturing vacuum level of -5.0 psig., with no pre-heating. See the results of Example 1 for this comparison (6.91 μL vs. 3.1 μL). The average volume of blood collected using a pre-heating duration of 60 seconds was approximately four times the average volume of blood collected at a post-puncturing vacuum level of -5.0 psig, with no pre-heating. See the results of Example 1 for this comparison (11.6 μL vs. 3.1 μL). Example 4 This example illustrates the effect that stretching the skin upwardly with a vacuum has on the extraction of blood. Each of four people had his forearm (dorsal forearm, middle of forearm) punctured eight times (at eight different positions on the forearm) with a "BD ULTRA-FINE" lancet in a "MEDISENSE" lancet assembly. Vacuum was applied for a period of 30 seconds prior to puncturing at -5.0 psig using two different vacuum fixtures. The first fixture was a 15 mm diameter vacuum fixture (i. e., a hollow cylindrical tube) used without a net strung across the opening of the tube. The second fixture was a 15 mm diameter vacuum fixture (i. e., a hollow cylindrical tube) used with a net strung across the opening of the tube. The net prevented skin from being raised up into the vacuum fixture. The same vacuum fixture used prior to puncturing was applied for a period of 30 seconds after puncturing. The fixture was held level with the plane of the skin. Four punctures were carried out per person per condition (without net, with net). Accordingly, it can be seen that a total of 32 runs were carried out. Blood was collected into capillary tubes. The amount of blood collected was determined by measuring the length of blood in the tubes. The percentage of collections in which the volume of blood collected exceeded 1.0 μL was calculated. Sensation of pain was also recorded. Blood collection results are set forth in TABLE IV. TABLE IV The pain results were as follows: pain of 1 = 94% pain of 2 = 6% pain of 3 = 0% The magnitude of the difference in volume of blood collected and success rates (i. e., percent of samples having > 1 μL of blood collected) between the condition of stretching the skin in combination with a vacuum and the condition of not stretching the skin in combination with a vacuum was unexpected. The pain scores were low. This example demonstrates that the combination of skin stretching and applied vacuum significantly increased the volume of blood extracted. Example 5 This example illustrates the effect the area of the extraction site has on the volume of blood collected. Each of four people had his forearm (dorsal forearm, middle of forearm) punctured at 32 different positions on the forearm with a "BD ULTRA-FINE" lancet in a modified "MEDISENSE" lancet assembly. The "MEDISENSE" lancet assembly had been modified with a more powerful spring and a port had been added. Vacuum was applied for less than five seconds prior to puncturing. The forearm was punctured under a vacuum of either -5.0 psig or -7.5 psig. The vacuum applied was maintained for 30 seconds after puncturing. The diameter of the pipette tip used to apply vacuum after puncturing was varied, with diameters of 4, 6, 8, and 10 mm being used. Four punctures per condition (diameter, vacuum level) were carried out per person. Accordingly, it can be seen that a total of 128 runs were carried out. Blood was collected into capillary tubes. The amount of blood collected was determined by measuring the length of blood in the tubes. The percentage of collections in which the volume of blood collected exceeded 1.0 μL was calculated. Sensation of pain was also recorded. Blood collection results are set forth in TABLE VA and VB. TABLE VA vacuum level = -5.0 psig TABLE VB vacuum level = -7.5 psig The pain results were as follows: pain of 1 = 89% pain of 2 = 10% pain of 3 = 1 % The volume of blood collected and success rates (i. e., percent of samples having > 1 μL of blood collected) were found to vary directly with the area of skin raised up into the device by the vacuum. A much greater volume of skin was raised up into the larger diameter pipette tip than into the smaller diameter pipette tips. Example 6 This example illustrates that a plastic multiple point lancet can be used with heat and vacuum to collect a useful amount of blood. Each of four people had his forearm (dorsal forearm, middle of forearm) punctured sixteen times (at sixteen different positions on the forearm) with a Greer Derma PIK® System for allergy testing (Greer Laboratories, Inc., Lenoir, North Carolina 28645) modified to fit into a "MEDISENSE" lancet assembly. Pre-heating was carried out at approximately 40 °C and 45 °C for 15 and 60 seconds prior to puncturing. Four punctures were carried out per condition (temperature, time) per person. Accordingly, it can be seen that a total of 64 runs were carried out. Heat was applied with a heating block, which comprised an aluminum block having one face covered with a "KAPTON" film heater element controlled by an "OMEGA" DP41 temperature controller using a T-type thermocouple and the opposite face in contact with the larger base of a frustum of a cone made of copper. The larger base of the frustum had a diameter of 0.50 in. The height of the frustum was 0.50 in. The smaller base of the frustum had a diameter of 0.35 in. The smaller base had a cylindrical opening having a diameter of 0.125 in. The cylindrical opening had a common axis with the frustum. The cylindrical opening reduced the heating surface of the copper frustum. Vacuum (-5.0 psig) was applied for a period of 30 seconds after puncturing. The vacuum in contact with the skin was formed by a pipette tip having a diameter of 8 mm. The pipette tip was held level with the plane of the skin. Blood was collected into capillary tubes. The amount of blood collected was determined by measuring the length of blood in the tubes. The percentage of collections in which the volume of blood collected exceeded 1.0 μL was calculated. Sensation of pain was also recorded. Blood collection results are set forth in TABLE VI. TABLE VI The pain results were as follows: pain of 1 = 100% pain of 2 = 0% pain of 3 = 0% This example demonstrates that a blood extraction process employing a multi-point plastic lancet, pre-piercing heating, skin stretching, and post-piercing vacuum can extract at least 1 μL of blood at least 50 % of the time. Example 7 A prototype of the lancing assembly of this invention was tested in vitro for kinematic performance, using a "BD ULTRA-FINE" brand lancet and a solenoid valve supplied by the Lee Co, Model No. LHDA0511111 H. Design parameters of the prototype are listed below. The definitions of these parameters were previously set forth. A = 30.7 mm 2 (diameter = 6.25 mm) M = 1.2 grams S = 10 mm Xp = n/a Ks = 19.5 N/m Xs = 8.7 mm C v = 0.015 Dt v = 0.7 msec V c = 0.01 cc V v = 5 cc P a = 14.7 psia (= 0 psig) P v = 6.7 psia (= -8.0 psig) T a = 25° C Ff = 0.13 N - 0.18 N This configuration resulted in good lancing results when tested on human subjects. The measured lancet speed at the end of the stroke was 2.7 m/sec. Example 8 Multiple-layer elements comprising the following layers, from top to bottom, were prepared: (1 ) meter-contactable layer (2) detecting layer (3) overcoat layer (4) blood-transporting layer (5) covering layer The arrangement of the layers is shown schematically in FIGS. 21 A and 21 B. However, the overcoat layer is substantially coplanar with the blood-transporting layer as shown in FIG. 28. The meter-contactable layer 1 114 was about 5.5 mm wide and about 40 mm long. The meter-contactable layer was made from polyvinyl chloride. A 1.5 mm diameter opening was punched in the meter-contactable layer. The detecting layer 1110 was screen printed on the meter-contactable layer. Across the opening in the meter-contactable layer was placed a layer of mesh, which served as the blood-transporting layer 1108. The mesh was the mesh previously identified as NY151 HC. The detecting layer 1110 was the type of detecting layer described in U. S. Patent No. 5,682,884. The overcoat layer 1123 was screen printed about the periphery of the layer of mesh. The covering layer 1102 was about 5.5 mm wide and somewhat shorter than the meter-contactable layer so that the electrical contacts 1110a of the detecting layer 1110 would be exposed. The covering layer was made from polyester. A 2.5 mm by 3.7 mm oval opening in the covering layer was punched prior to assembly of the multiple-layer element. The multiple-layer element was placed in the apparatus as shown in FIGS. 29A, 29B, 29C, and 29D. A vacuum of -7.5 psig was applied. The apparatus was placed in contact with the forearm of a volunteer who was diabetic. See FIG. 29A. The skin of the forearm was stretched and it raised up into the nosepiece, where it came near to or into contact with the covering layer 1102 of the multiple-layer element. See FIG. 29B. After the vacuum had been applied for five seconds, the lancet was fired into the skin by means of a spring-powered lancet assembly. The lancet passed through the opening 1116 in the meter-contactable layer 1114 and the opening 1104 in the covering layer 1102. See FIG. 29C. The lancet was retracted and blood began to emerge from the forearm of the diabetic volunteer. The vacuum aided in the extraction of blood until the blood reached the layer of mesh 1108. See FIG. 29D. The blood was then transported along the mesh until it reached the detecting layer 1110 of the multiple-layer element. When the blood reached the detecting layer of the multiple-layer element, an electrical current was generated. This current was used to determine when to release the vacuum. The electrical current was also an indication of the level of glucose in the blood of the volunteer. Seven diabetic volunteers were tested as described in the previous paragraph. The time required for the multiple-layer element to fill after the lancing operation was recorded. The multiple-layer element was considered to be filled when a current of 1.5 μA was generated. The vacuum was then released and the current was recorded for 20 seconds. During the last five seconds of the 20 second measurement period, the current was integrated. The integrated current (i. e., charge) was recorded. The lancing procedure and data collection were repeated four times per volunteer. All 28 lancing procedures resulted in blood filling the multiple-layer element in less than 40 seconds. The average time required to fill the multiple-layer element was 7 seconds. FIG. 30 shows the average charge of the four trials as a function of the level of glucose in the blood of each volunteer. The level of glucose was determined by withdrawing blood from a finger and measuring the level of glucose on a YSI 2300 Glucose analyzer. The charge increased linearly with the level of glucose in the blood of the volunteer. The volunteers were asked to rate the pain of the forearm lancet. The pain of the forearm lancet was found to be lower than the pain of the finger lancet, as shown in FIG. 31. Example 9 Multiple-layer elements comprising the following layers, from top to bottom, were prepared: (1 ) meter-contactable layer (2) detecting layer (3) overcoat layer (4) blood-transporting layer (5) covering layer The arrangement of the layers is shown schematically in FIGS. 21 A and 21 B. However, the overcoat layer is substantially coplanar with the blood-transporting layer as shown in FIG. 28. The meter-contactable layer 1114 was about 5.5 mm wide and about 40 mm long. The meter-contactable layer was made from polyester. A 2.0 mm diameter opening was punched in the meter-contactable layer. The detecting layer 1110 was screen printed on the meter-contactable layer. Across the opening in the meter-contactable layer was placed a layer of mesh, which served as the blood-transporting layer 1108. The mesh was the mesh previously identified as NY151 HC. A section of the mesh (1.5 mm in diameter) was punched out by means of a hole punch. See FIG. 25. The detecting layer 1110 was the type of detecting layer described in U. S. Patent No. 5,682,884. The overcoat layer 1123 was screen printed about the periphery of the layer of mesh. The covering layer 1102 was about 5.5 mm wide and somewhat shorter than the meter-contactable layer so that the electrical contacts 1110a of the detecting layer 1110 would be exposed. The covering layer was made from polyester. A 2.5 mm by 3.7 mm oval opening in the covering layer was punched prior to assembly of the multiple-layer element. The multiple-layer element was placed in the apparatus as shown in FIGS. 29A, 29B, 29C, and 29D. A vacuum of -7.5 psig was applied. The apparatus was placed in contact with the forearm of a volunteer. See FIG. 29A. The skin of the forearm was stretched and it raised up into the nosepiece, where it came near to or into contact with the covering layer 1102 of the multiple- layer element. See FIG. 29B. After the vacuum had been applied for five seconds, the lancet was fired into the skin by means of a pneumatic lancing assembly of the type shown in FIGS. 11 , 12, 13, and 14. The lancet passed through the opening 1116 in the meter- contactable layer 1114 and the opening 1104 in the covering layer 1102. See FIG. 29C. The lancet was retracted and blood began to emerge from the forearm of the volunteer. The vacuum aided in the extraction of blood until the blood reached the mesh 1108. See FIG. 29D. The blood was then transported along the mesh until it reached the detecting layer 1110 of the multiple-layer element. When the blood reached the detecting layer of the multiple-layer element, an electrical current was generated. This current was used to determine when to release the vacuum. Eight volunteers were tested as described in the previous paragraph. The time required for the multiple-layer element to fill after the lancing operation was recorded. The multiple-layer element was considered to be filled when a current of 1.5 μA was generated. The vacuum was then released and the integrated current was recorded. The lancing procedure and data collection were repeated four times per volunteer. Blood filled the multiple-layer element in less than 40 seconds for 97% of the tests. The average time required to fill the multiple-layer element was 15.9 seconds. Example 10 Multiple-layer elements comprising the following layers, from top to bottom, were prepared: (1 ) meter-contactable layer (2) detecting layer (3) overcoat layer (4) blood-transporting layer (5) covering layer The arrangement of the layers is shown schematically in FIGS. 21 A and 21 B. However, the overcoat layer is substantially coplanar with the blood-transporting layer as shown in FIG. 28. The meter-contactable layer 1114 was about 5.5 mm wide and about 40 mm long. The meter-contactable layer was made from polyester. Two types of meter-contactable layers were prepared. In the first type, one opening was punched in the meter-contactable layer. This opening had a diameter of 2.0 mm. No mesh was placed across this opening. See FIG. 26B. In the second type, two openings were punched in the meter-contactable layer. One opening had a diameter of 2.0 mm. The other opening had a diameter of 1.5 mm. The second opening was located 2 mm from the first opening. See FIG. 26A. The detecting layer 1110 was screen printed on the meter-contactable layer. Across the 1.5 mm opening in the meter-contactable layer was placed a layer of mesh, which served as the blood-transporting layer 1108. The mesh was the mesh previously identified as NY151 HC. The detecting layer 1 110 was the type of detecting layer described in U. S. Patent No. 5,682,884. The overcoat layer 1123 was screen printed about the periphery of the layer of mesh. The covering layer 1102 was about 5.5 mm wide and somewhat shorter than the meter-contactable layer so that the electrical contacts 1110a of the detecting layer 1110 would be exposed. The covering layer was made from polyester. A 2.5 mm by 3.7 mm oval opening in the covering layer was punched prior to assembly of the multiple-layer element. The multiple-layer element was placed in the apparatus as shown in FIGS. 29A, 29B, 29C, and 29D. A vacuum of -7.5 psig was applied. The apparatus was placed in contact with the forearm of a volunteer. See FIG. 29A. The skin of the forearm was stretched and it raised up into the nosepiece, where it came near to or into contact with the covering layer 1 102 of the multiple-layer element. See FIG. 29B. After the vacuum had been applied for five seconds, the lancet was fired into the skin by means of a pneumatic lancet assembly. This pneumatic lancet assembly was the assembly shown in FIGS. 16 and 17. The lancet passed through the 2.0 mm opening 1116 in the meter- contactable layer 1114 and the opening 1104 in the covering layer 1102. See FIG. 29C. The lancet was retracted and blood began to emerge from the forearm of the volunteer. See FIG. 29D. As quickly as possible, the multiple-layer element was slid approximately 2 mm in the direction away from the electrical contacts. This type of movement is more fully described in the discussion of FIGS. 46A through 46C. The movement of the multiple-layer element caused the site of the opening in the skin to be in vertical alignment with the mesh 1108 of the multiple-layer element. In the case of the meter-contactable layer having two openings, this was the site of the opening 1122 that was 1.5 mm in diameter. The vacuum aided in the extraction of blood until the blood reached the mesh 1108. The blood was then transported along the mesh until it reached the detecting layer 1110 of the multiple- layer element. When the blood reached the detecting layer 1110 of the multiple- layer element, an electrical current was generated. This current was used to determine when to release the vacuum. Nine non-diabetic volunteers were tested as described in the previous paragraph. Each volunteer was tested with each type of multiple-layer element. The time required for the multiple-layer element to fill after the lancing operation was recorded. The multiple-layer element was considered to be filled when a current of 1.5 μA was generated. The vacuum was then released. The lancing procedure and data collection were repeated eight times per volunteer per element. Blood filled the multiple-layer element having one opening in the meter- contactable layer in less than 40 seconds for 95% of the tests. Blood filled the multiple-layer element having two openings in the meter-contactable layer in less than 40 seconds for 96% of the tests. The average time required to fill the multiple- layer element having two openings in the meter-contactable layer was 14 seconds. The average time required to fill the multiple-layer element having one opening in the meter-contactable layer was 11 seconds. Example 11 This example illustrates the effect of the size and the shape of the nosepiece upon the volume of blood extracted. Each of 21 volunteers was tested thirty times in the dorsal forearm by a modified MediSense lancing assembly employing a "BD ULTRA-FINE" lancet (Becton-Dickinson). The MediSense lancing assembly had been modified with a port to allow a vacuum to effect suction through the lancing assembly. The nosepieces tested in this example were screwed onto the body of a MediSense lancing assembly in place of the conventional nosepiece. Vacuum (-7.5 psig) was applied for 10 seconds prior to lancing. After lancing, blood was collected for 30 seconds at -7.5 psig. The same nosepiece that was used prior to lancing was used for blood collection. The openings formed in the skin had a depth of 1.6 mm. Fifteen different nosepiece assemblies were evaluated. These assemblies are shown in FIG. 33. The diameter of the opening in the lower base of the nosepiece (see line "ef" in FIG. 32) varied from 9.53 to 19.05 mm. The diameter of the opening in the lower base of the nosepiece for nosepiece assemblies 1 , 2, and 3 was 9.53 mm. The diameter of the opening in the lower base of the nosepiece for nosepiece assemblies 4, 5, 6, and 7 was 12.70 mm. The diameter of the opening in the lower base of the nosepiece for nosepiece assemblies 8, 9, 10, and 11 was 15.88 mm. The diameter of the opening in the lower base of the nosepiece for nosepiece assemblies 12, 13, 14, and 15 was 19.05 mm. The rim-to-seal distances for the nosepieces (see line "bg" in FIG. 32) varied from 1.6 mm to 6.0 mm. The rim-to-seal distance for nosepieces 1 , 4, 8, and 12 was 1.6 mm. The rim- to-seal distance for nosepieces 2, 5, 9, and 13 was 3.0 mm. The rim-to-seal distance for nosepieces 3, 6, 10, and 14 was 4.5 mm. The rim-to-seal distance for nosepieces 7, 11 , and 15 was 6.0 mm. The nosepieces shown in FIG. 33 had seals made from Buna N rubber. The thickness of the seals (see line "eh" in FIG. 32) was 1.6 mm and the width of the sealing surface (see line "hj" in FIG. 32) was 3.1 mm. The nosepieces had vertical walls. Two tests were conducted per nosepiece assembly per volunteer. Blood was collected into capillary tubes. The amount of blood collected was determined by measuring the distance the blood travelled into the tube. The average amount of blood collected for each of the fifteen assemblies and the percentage of collections in which the amount of blood exceeded 1.0 μL was calculated. The results are set forth in TABLE VII. TABLE VII The volume of blood collected and the percentage of collections exceeding 1 μL were both affected by the diameter of the opening in the lower base of the nosepiece and the rim-to-seal distance of the nosepiece. Large increases in the volume of blood collected were seen with nosepiece assemblies 6 and 7. Example 12 This example illustrates the effect of tapering the interior wall of the nosepiece upon the time to draw blood from a person. Glucose detectors in the form of multiple-layer elements comprising the following layers, from top to bottom, were prepared: (1 ) meter-contactable layer (2) detecting layer (3) overcoat layer (4) blood-transporting layer (5) covering layer The arrangement of the layers is shown schematically in FIGS. 21 A and 21 B. However, the overcoat layer is substantially coplanar with the blood-transporting layer as shown in FIG. 28. The use of a nosepiece with a detector is shown in FIGS. 34A, 34B, 34C, and 34D. The detector 1302 was placed below the lancing assembly 1304 with the openings in the detector aligned with the lancet 1306. The detector 1302 was placed between a lancet stop 1308 that contained an opening 1309 (shown in phantom) and a nosepiece assembly 1310. The nosepiece assembly included a nosepiece 1311 and a seal 1312 that contacted the skin "S". The lancing assembly 1304 prior to the application of vacuum is shown in FIG. 34A. The nosepiece assembly was placed against the forearm of a volunteer. After application of vacuum (-7.5 psig), the skin was stretched up near to or into contact with the detector as shown in FIG. 34B. The vacuum was applied for a sufficient amount of time (5 seconds) to cause the blood in the skin inside the nosepiece to pool. The lancet was then fired through the openings in the lancet stop and the detector, as shown in FIG. 34C. The lancet penetrated the skin. The lancet was then retracted as shown in FIG. 34D. The blood emerged from the opening formed in the skin, assisted by the vacuum and the stretching of the skin. The vacuum aided in the extraction of blood until the blood reached the blood-transporting layer. The blood "B" was then transported along the blood-transporting layer until it reached the detecting layer of the multiple-layer element. When the blood reached the detecting layer of the multiple-layer element, an electrical current was generated. This current was used to determine when to release the vacuum, and the skin came away from the nosepiece. The detector could then be used to analyze the blood for an analyte such as glucose. It should be noted that the lancet stop is optional. The detector itself can be used to stop the lancet. If the detector is used to stop the lancet, the thickness of the detector is important, because it will determine the depth of penetration of the lancet. The type of multiple-layer element used in this example had one opening in the meter-contactable layer, as shown in FIGS. 21 A and 21 B. Five varieties of nosepieces were used in this example. These nosepieces are shown in cross-section in FIG. 35. The nosepieces varied in the areas of the opening in the upper base, and the distance from the lower base at which tapering of the interior wall began. The diameters "d" of the openings in the upper base for each nosepiece was as follows: The rim-to-seal distance (see line "bg" in FIG. 32), 4.5 mm, and the diameter of the opening in the lower base of the nosepiece (see line "ef" in FIG. 32), 12.7 mm, was the same for all five nosepieces. The nosepiece assemblies shown in FIG. 35 had seals made from Buna N rubber, 40A durometer hardness. The thickness of the seals (see line "eh" in FIG. 32) was 1.6 mm, and the width of the sealing surface (see line "hj" in FIG. 32) was 3.1 mm Eight volunteers were tested as described above. Each volunteer was tested 10 times with nosepiece A and four times with each of the remaining nosepieces, B, C, D, and E in FIG. 35. The time required for the multiple-layer element to fill was recorded. The element was considered filled when a current of 1.5 microamperes (μA) was generated by the element. The vacuum was then released. The average time required to reach 1.5 μA for each nosepiece was calculated and is shown in FIG. 36. The smaller the diameter of the opening in the upper base, the less time was required to fill the detector. Example 13 This example illustrates the effect of tapering the interior wall of the nosepiece upon the time to draw blood and the success of drawing blood from a volunteer from whom drawing blood was typically difficult. The experiment was conducted as described in Example 12 with the following exceptions. Only nosepieces having the configurations of nosepieces A and B were used in the example. The diameter of the opening in the upper base on nosepiece B was four millimeters instead of the three millimeter opening used in Example 12. The volunteer was tested 10 times using nosepiece A. The volunteer was also tested 10 times with nosepiece B. The average time required to fill the multiple-layer element was calculated for elements that filled in 40 seconds or less and is shown in FIG. 37. The percentage of multiple-layer elements that filled in 40 seconds or less was calculated and is shown in FIG. 38. The nosepiece having the opening in the upper base having a diameter of less than the diameter of the opening in the lower base, nosepiece B, filled in less than half the time required by a nosepiece where the diameter of the opening in the upper base was equal to the diameter of the opening in the lower base, nosepiece A. The percentage of multiple-layer elements that were filled in under 40 seconds was significantly improved for nosepiece B, as compared with nosepiece A. Example 14 This example illustrates the effect of the shape of the opening in the upper base upon the time required to draw blood from a person. Glucose detectors in the form of multiple-layer elements comprising the following layers, from top to bottom, were prepared: (1 ) meter-contactable layer (2) detecting layer (3) overcoat layer (4) blood-transporting layer (5) covering layer The arrangement of the layers is shown schematically in FIGS. 21 A and 21 B. However, the overcoat layer is substantially coplanar with the blood-transporting layer as shown in FIG. 28. The use of a nosepiece with a detector is shown in FIGS. 34A, 34B, 34C, and 34D. The detector 1302 was placed below the lancing assembly 1304 with the openings in the detector aligned with the lancet 1306. The detector 1302 was placed between a lancet stop 1308 that contained an opening 1309 (shown in phantom) and a nosepiece assembly 1310. The nosepiece assembly 1310 included a nosepiece 1311 and a seal 1312 that contacted the skin "S". The lancing assembly 1304 prior to the application of vacuum is shown in FIG. 34A. The nosepiece assembly 1304 was placed against the forearm of a volunteer. After application of vacuum (-7.5 psig), the skin was stretched up near to or into contact with the detector as shown in FIG. 34B. The vacuum was applied for a sufficient amount of time (5 seconds) to cause the blood in the skin inside the nosepiece to pool. The lancet was then fired through the openings in the lancet stop and the detector, as shown in FIG. 34C. The lancet penetrated the skin. The lancet was then retracted, as shown in FIG. 34D. The blood emerged from the opening formed in the skin, assisted by the vacuum and the stretching of the skin. As quickly as possible, the multiple-layer element was slid approximately 2 mm in the direction away from the electrical contacts. This type of movement is more fully described in the discussion of FIGS. 46A through 46C. The vacuum aided in the extraction of blood until the blood reached the blood-transporting layer. The blood "B" was then transported along the blood-transporting layer until it reached the detecting layer of the multiple-layer element. When the blood reached the detecting layer of the multiple-layer element, an electrical current was generated. This current was used to determine when to release the vacuum, and the skin came away from the nosepiece. The detector could then be used to analyze the blood for an analyte such as glucose. It should be noted that the lancet stop is optional. The detector can be used to stop the lancet. If the detector is used to stop the lancet, the thickness of the detector is important, because it will determine the depth of penetration of the lancet. The type of multiple-layer element used in this example had two openings in the meter-contactable layer, as shown in FIG. 26A. A pneumatic lancing assembly was used to fire the lancet. The pneumatic lancing assembly was the type of lancing assembly described in FIGS. 16 and 17. Five variations of nosepiece assemblies were used in this example. They are shown in top view and cross section in FIG. 39. The nosepieces varied in the depth of the rim (see line "ab" in FIG. 32) and the shape of the opening in the upper base. The rim-to-seal distance plus the depth of the rim, 4.0 mm, (see line "bg" plus line "ab" in FIG. 32) and the diameter of the opening in the lower base of the nosepiece, 12.7 mm, (see line "ef" in FIG. 32) was the same for all five nosepieces. Eight volunteers were tested on the dorsal forearm as described above. Each volunteer was tested four times with each of the five nosepieces, for a total of 20 tests per volunteer. The time for the detector to fill after lancing was recorded. The detector was considered filled when a current of 1.5 μA was generated. The vacuum was then released. The average time required to reach a current of 1.5 μA for the five nosepieces was calculated and is shown in TABLE VIII. TABLE VIII The nosepieces as shown in FIG. 39 had seals made from Buna N rubber, 40A durometer. The thickness of the seal (see line "eh" in FIG. 32) was 1.6 mm and the width of the sealing surface (see line "hj" in FIG. 32) was 3.1 mm. For a given opening shape, the nosepieces having rims of lower depth required less time to fill the detector than did those nosepieces having rims of greater depth. For a given depth of rim, the nosepieces having oval rim openings required less time to fill the detector than did nosepieces having circular rim openings. Example 15 This example illustrates the effect of different sealing materials upon the ability to form a good vacuum seal to a hairy arm. Seals were punched out from sheets of different sealing materials. The eight materials used are listed in TABLE IX. The seals, which were circular in shape, had a sealing surface width (see line "hj" in FIG. 32) of 3.1 mm. Each seal was then utilized in a nosepiece, as shown in FIG. 32. The seals were attached to the lower base of the nosepiece by means of an adhesive. The distance from the rim to the lower base of nosepiece prior to attachment of the seal was 1.5 mm. After the attachment of the seal, the rim-to-seal distance of the nosepiece was variable due to the differences in the thickness of the seal. A vacuum port was attached to the nosepiece to allow a vacuum source to effect suction through the nosepiece. An air flow meter (Alicat Scientific, Tucson, Arizona, Model #PVM200SCCM-D-S-A) was attached between the vacuum source and the nosepiece. The nosepiece was attached to a holder. The combined weight of the nosepiece and holder was 230 grams. A male volunteer who had more hair on his dorsal forearm than did the average male population was chosen. The volunteer placed his arm against the seal of the nosepiece so as to bring the full weight of the nosepiece and holder against the arm. The purpose of this apparatus was to provide a constant pressure. A vacuum of -8 psig was applied. The ability of the seal to seal to the skin was measured by the amount of air leaking into the nosepiece, as measured by the air flow meter in the units of standard cubic centimeters per minute (SCCM). The measurement was repeated at a total of 20 locations on the volunteer's forearm for each of the seal types. The average leakage rate at the twenty forearm sites for each of the seal materials is shown in FIG. 40. All the materials were capable of limiting the average leakage rate to below 40 SCCM on the volunteer. The leakage rate is important because the size of the vacuum pump required is directly proportional to the leakage rate. In addition, a low leakage rate will result in improved battery life. A small vacuum pump can be used at a low leakage rate. The low leakage rates obtained allow a commercially available miniature vacuum pump, such as that available from T-Squared Manufacturing Company, Nutley, NJ, and having the part number T2-03.08.004, to be used with the apparatus. The low leakage rates obtained with the seal materials tested mean that cumbersome methods of attaching the nosepiece to the skin to achieve a good seal are not needed. Other methods to attach the nosepiece to the skin to form a vacuum seal are not preferred. An adhesive is not preferred because it will make the nosepiece assembly difficult to remove, and it can cause pain to the user when the seal is removed. Grease is not preferred because it will leave a residue after the test is complete. TABLE IX Example 16 This example illustrates the effect of different sealing materials upon the amount of blood extracted from a person. Each of four volunteers was tested 32 times in the dorsal forearm by a modified MediSense lancing assembly employing a "BD ULTRA-FINE" lancet. The MediSense lancing assembly had been modified with a port to allow a vacuum to effect suction through the lancing assembly. The nosepieces tested in this example were screwed onto the body of a MediSense lancing assembly in place of the conventional nosepiece. Vacuum (-7.5 psig) was applied for five seconds prior to lancing. Blood was collected after lancing for 30 seconds at -7.5 psig using the same nosepiece as was used prior to lancing. The depth setting of the lancet was 1.6 mm. Eight different nosepiece assemblies were evaluated. Four tests were conducted per nosepiece assembly per volunteer. Blood was collected into capillary tubes. The amount of blood collected was determined by measuring the length of blood in the tube. The average amount of blood collected for each of the eight nosepiece assemblies is shown in FIG. 41. For the eight different nosepiece assemblies, the diameter of the opening in the lower base (see line "ef" in FIG. 32) was 10 mm, the diameter of the opening in the upper base (see line "cd" in FIG. 32) was 4 mm, the rim-to-seal distance (see line "bg" in FIG. 32) was 3 mm, and the width of the sealing surface (see line "hj" in FIG. 32) was 3.1 mm. The nosepiece assemblies differed in the material used for the nosepiece seal and the thickness of the seal. The eight variations of sealing material and thicknesses thereof are listed in TABLE X. TABLE X All of the eight different nosepiece seal materials sealed well enough to the skin to enable the extraction of on average greater than 3 μL of blood in 30 seconds. The hardest material of the eight tested, Buna N - 60A durometer, had the highest blood extraction rate. Increasing the seal thickness from 1.6 to 3.2 mm had little effect on the volume of blood collected in 30 seconds. Example 17 This example illustrates the effect of using a novel seal upon the time required to extract blood from a person. Glucose detectors in the form of multiple-layer elements comprising the following layers, from top to bottom, were prepared: (1 ) meter-contactable layer (2) detecting layer (3) overcoat layer (4) blood-transporting layer (5) covering layer The arrangement of the layers is shown schematically in FIG. 21 A and 21 B. However, the overcoat layer is substantially coplanar with the blood-transporting layer as shown in FIG. 28. The use of a nosepiece with a detector is shown in FIGS. 34A, 34B, 34C, and 34D. The detector 1302 was placed below the lancing assembly 1304 with the openings in the detector aligned with the lancet 1306. The detector 1302 was placed between a lancet stop 1308 that contained an opening 1309 (shown in phantom) and a nosepiece assembly 1310. The nosepiece assembly 1310 included a nosepiece 1311 and a seal 1312 that contacted the skin "S". The lancing assembly 1304 prior to the application of vacuum is shown in FIG. 34A. The nosepiece assembly was placed against the forearm of a volunteer. After application of vacuum (-7.5 psig), the skin was stretched up near to or into contact with the detector as shown in FIG. 34B. The vacuum was applied for a sufficient amount of time (5 seconds) to cause the blood in the skin inside the nosepiece to pool. The lancet was then fired through the openings in the lancet stop and the detector, as shown in FIG. 34C. The lancet penetrated the skin. The lancet was then retracted, as shown in FIG. 34D. The blood emerged from the opening formed in the skin, assisted by the vacuum and the stretching of the skin. The vacuum aided in the extraction of blood until the blood reached the blood-transporting layer. The blood "B" was then transported along the blood-transporting layer until it reached the detecting layer of the multiple-layer element. When the blood reached the detecting layer of the multiple-layer element, an electrical current was generated. This current was used to determine when to release the vacuum, and the skin came away from the nosepiece. The detector could then be used to analyze the blood for an analyte such as glucose. It should be noted that the lancet stop is optional. The detector itself can be used to stop the lancet. If the detector is used to stop the lancet, the thickness of the detector is important, because it will determine the depth of penetration of the lancet. A pneumatic lancing assembly was used to fire the lancet. The pneumatic lancing assembly was the type of lancing assembly described in FIGS. 11 , 12, 13, and 14. The type of multiple-layer element used in this example had one opening in the meter-contactable layer, as shown in FIGS. 21 A and 21 B. Two nosepiece assembly variations were used in this example. The size and structure of both nosepieces in the nosepiece assemblies were the same as that of nosepiece B of FIG. 35, with the exception that the diameter of the opening in the upper base was increased to 4 mm. One nosepiece had a planar Buna N seal, 40 durometer (see FIG. 32). The other nosepiece had a seal of the type shown in FIGS. 21 A and 21 B in cross section, referred to hereinafter as a flex seal. The flex seal contacts a larger area of skin then does a planar seal. The flex seal can then cause more skin to be brought into the internal space of the nosepiece when vacuum is applied than can a planar seal. The flex seal was made out of a silicone, 40A durometer. The flex seal 3020 can be attached to the nosepiece 3022 by a mechanical attachment 3024 or by an adhesive. The portion 3026 of the flex seal that is not attached to the nosepiece 3022 is capable of moving between a first position, as shown in FIG. 42A, and a second position, as shown in FIG. 42B. In the first position, the unattached portion 3026 of the flex seal 3020 depends from the lower base 3028 of the nosepiece 3022 as shown in FIGS. 42A. In the second position, the unattached portion 3026 of the flex seal 3020 contacts the lower base 3028 of the nosepiece 3022 such that one major surface of the unattached portion of the seal is in face-to-face contact with the lower base 3028 of the nosepiece as shown in FIG. 42B. The flex seal is made of a material having a coefficient of friction that reduces the tendency of skin in contact with it to slide. The seal should be sufficiently flexible so that it can move between the first position and the second position and sufficiently stiff to hold the skin in an immovable position. The opening 3030 in the flex seal has an area greater than the area of the opening 3032 in the lower base 3028 of the nosepiece 3022, when the flex seal is in the first position, as shown in FIG. 42A. In operation, the flex seal, is placed against the skin "S" of the patient. The area of skin contacted by the flex seal is greater than the area of the opening in the lower base of the nosepiece. Consequently, the volume of skin lifted into the nosepiece is greater than the volume of skin that would have been lifted into the nosepiece with a planar seal. Thus, the flex seal would be beneficial for a patient having below normal skin flexibility. Eight volunteers were tested on the dorsal forearm substantially in the manner described previously. In the previous examples, the nosepiece assembly was manipulated by moving it from side to side or toward and away from the skin. In this example, the nosepiece assembly was not moved after it was placed against the skin. Each volunteer was tested eight times using the planar seal and flex seal configurations for a total of 16 tests per volunteer. The time to fill the detector after lancing was recorded. The detector was considered filled when a current of 1.5 μA was generated. The vacuum was then released. The average time required for the current to reach 1.5 μA for the flex seal was 14.9 seconds and the average time required for the current to reach 1.5 μA for the planar seal was 17.9 seconds. The nosepiece employing the flex seal required less time to fill the detector than did the nosepiece employing a planar seal. Moreover, manipulation of the nosepiece assembly was eliminated. Example 18 This example demonstrates that the device shown in FIGS. 44A and 44B can be used successfully to obtain blood in quantities sufficient for analysis in an acceptably short amount of time. The blood collection device shown in FIGS. 44A and 44B was fitted with a "Becton-Dickinson ULTRA-FINE" lancet in a pneumatic lancet assembly of the type illustrated in FIGS. 11-19. The blood collection device was also fitted with a glucose detector having a 2.0 mm diameter opening covered with mesh. Twenty- nine human volunteers were used in this example, with the dorsal forearm of each volunteer subjected to two separate extraction procedures. For each procedure, the blood collection device was placed against the forearm of the volunteer and, after being exposed to a vacuum of approximately -7.5 psig for approximately 5 seconds, each individual had his or her forearm (dorsal forearm) punctured. After the puncture, blood was collected and, when a sufficient amount of blood had been collected, the vacuum was released and the blood collection device was removed from the individual's skin. This process was repeated a total of two times for each individual. Prior to each extraction, a new lancet and glucose detector were fitted into the blood collection device. The time for the glucose detector to collect sufficient blood to perform an analysis was recorded. The glucose detector was considered to have collected sufficient blood when a current of 1.5 μA was generated. Blood collection results are set forth in FIG. 47. The raw data graphically depicted in FIG. 47 is shown for each volunteer in Table XI. TABLE XI The data depicted in FIG. 47 shows that, for over 35% of the punctures, sufficient blood was collected within five seconds to perform an analysis. With the exception of one glucose detector that malfunctioned (volunteer 25, trial 2), for approximately 95% of the punctures, the glucose detectors collected sufficient blood in 40 seconds or less for analysis. For the remaining punctures, the tests were stopped after 40 seconds. With respect to those punctures for which sufficient blood was collected in 40 seconds or less, the average time to collect sufficient blood was 8.2 seconds. Example 19 This example demonstrates that the device shown in FIGS. 43A through 43C can be successfully used to obtain blood in quantities sufficient for analysis in an acceptably short amount of time. The blood collection device shown in FIGS. 43A through 43C was fitted with a "BD ULTRA-FINE" lancet in a pneumatic lancet assembly of the type illustrated in FIGS. 11 -19. The blood collection device was also fitted with a glucose detector having a 2.0 mm diameter opening covered with mesh. Fifteen human volunteers were used in this example, with the dorsal forearm of each volunteer subjected to four separate extraction procedures. For each procedure, the blood collection device was placed against the forearm of the volunteer and, after being exposed to a vacuum of approximately -7.5 psig for approximately 5 seconds, each individual had his or her forearm (dorsal forearm) punctured. After the puncture, blood was collected and, when a sufficient amount of blood had been collected, the vacuum was released and the blood collection device was removed from the individual's skin. This process was repeated a total of four times for each individual. Prior to each extraction, a new lancet and glucose detector were fitted into the blood collection device. The time for the glucose detector to collect sufficient blood to perform an analysis was recorded. The glucose detector was considered to have collected sufficient blood when a current of 1.5 μA was generated. Blood collection results are set forth in FIG. 48. The data depicted in FIG. 48 show that, for approximately 45% of the punctures, sufficient blood was collected within five seconds to perform an analysis. For approximately 97% of the punctures, the glucose detectors collected sufficient blood in 40 seconds or less for analysis. For the remaining punctures, the tests were stopped after 40 seconds. With respect to those punctures for which sufficient blood was collected in 40 seconds or less, the average time to collect sufficient blood was 7.0 seconds. Example 20 This example demonstrates that the device shown in FIGS. 45A through 45E can be successfully used to obtain blood in quantities sufficient for analysis in an acceptably short amount of time. The blood collection device shown in FIGS. 45A through 45E was fitted with a "BD ULTRA-FINE" lancet in a pneumatic lancet assembly of the type illustrated in FIGS. 11 -19. The blood collection device was also fitted with a glucose detector having a 2.0 mm diameter semi-circular notch covered with mesh at one end of the detector. Twenty-nine human volunteers were used in this example, with the dorsal forearm of each volunteer subjected to two separate extraction procedures. For each procedure, the blood collection device was placed against the forearm of the volunteer and, after being exposed to a vacuum of approximately -7.5 psig for approximately 5 seconds, each individual had his or her forearm (dorsal forearm) punctured. Fifty milliseconds after the lancet was triggered, the movable projection was triggered and the glucose detector was moved nearer the lanced opening in the individual's skin. After the puncture, blood was collected and, when a sufficient amount of blood had been collected, the vacuum was released and the blood collection device was removed from the individual's skin. This process was repeated a total of two times for each individual. Prior to each extraction, a new lancet and glucose detector were fitted into the blood collection device. The time for the glucose detector to collect sufficient blood to perform an analysis was recorded. The glucose detector was considered to have collected sufficient blood when a current of 1.5 μA was generated. Blood collection results are set forth in FIG. 49. The data depicted in FIG. 49 show that for over 55% of the punctures, sufficient blood was collected within 5 seconds to perform an analysis. Two of the glucose detectors did not exceed the trigger current of 1.5 μA due to hardware or software problems. Two of the glucose detectors did not move due to an unknown problem and did not contact the skin. Excluding these four punctures, for 91 % of the remaining punctures, the glucose detectors collected sufficient blood in 40 seconds or less for analysis. For the remaining punctures, the tests were stopped after 40 seconds. With respect to those punctures for which sufficient blood was collected in 40 seconds or less, the average time to collect sufficient blood was 6.8 seconds. Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.

Claims: What is claimed is: 1. A method for obtaining a sample of blood for a diagnostic test, said method comprising the steps of: (a) forming an unobstructed opening in an area of skin from which said sample is to be extracted; (b) extracting said sample from said unobstructed opening in said area of said skin, with the aid of vacuum and stretching of the skin. 2. The method of claim 1 , wherein said diagnostic test is a test to determine the concentration of glucose in blood. 3. The method of claim 1 , further comprising the step of increasing the availability of blood to said area of said skin from which said sample is to be extracted prior to forming said opening in said area of said skin from which said sample is to be extracted. 4. The method of claim 3, wherein a vacuum is used to increase the availability of blood to said area of said skin from which said sample is to be extracted prior to forming said opening in said area of said skin from which said sample is to be extracted. 5. The method of claim 4, wherein stretching is used to increase the availability of blood to said area of said skin from which said sample is to be extracted prior to forming said opening in said area of said skin from which said sample is to be extracted. 6. The method of claim 3, wherein heat is used to increase the availability of blood to said area of said skin from which said sample is to be extracted prior to forming said opening in said area of said skin from which said sample is to be extracted. 7. The method of claim 6, wherein heat is used to increase the availability of blood to said area of said skin from which said sample is to be extracted prior to forming said opening in said area of said skin from which said sample is to be extracted. 8 The method of claim 1 , wherein said opening in said area of said skin from which the sample is to be extracted is formed by a lancet. 9. The method of claim 8, wherein said lancet is cocked by means of a vacuum. 10. The method of claim 8, wherein said lancet is triggered by means of a vacuum. 11. The method of claim 1 , wherein said extracted sample is analyzed by means of a glucose detector. 12. The method of claim 1 1 , wherein said glucose detector employs a reflectometer. 13. The method of claim 11 , wherein said glucose detector employs a biosensor. 14. The method of claim 8, wherein said lancet penetrates said skin to a depth of no more than 1.6 mm. 15. The method of claim 1 , wherein said opening in said area of said skin from which the sample is to be extracted is formed by a laser. 16. The method of claim 1 , wherein said opening in said area of said skin from which the sample is to be extracted is formed by a fluid jet. 17. The method of claim 1 , wherein said blood is obtained from a forearm. 18. The method of claim 1 , wherein said blood is obtained at a pain level lower than that experienced when a finger is pierced by a standard finger lancet. 19. An apparatus for suitable for obtaining a sample of body fluid for analysis in a diagnostic test, said apparatus comprising: (a) a device for forming an unobstructed opening in an area of skin from which said sample is to be extracted; and (b) a vacuum pump for extracting said sample from said unobstructed opening in said area of said skin. 20. The apparatus of claim 19, further including a housing. 21. The apparatus of claim 19, wherein said device for forming said unobstructed opening comprises a lancet disposed in a lancing assembly. 22. The apparatus of claim 21 , wherein said lancing assembly comprises a nosepiece having a seal, whereby a vacuum can be formed through the lancing assembly by said vacuum pump. 23. The apparatus of claim 19 wherein said lancet is capable of being retracted after it forms said unobstructed opening in said skin. 24. The apparatus of claim 19, wherein said device for forming said unobstructed opening is a laser. 25. The apparatus of claim 19 wherein said device for forming said unobstructed opening is a fluid jet. 26. The apparatus of claim 19, further comprising a heating element. 27. The apparatus of claim 19, further comprising a glucose detector. 28. The apparatus of claim 27, wherein said glucose detector is a biosensor. 29. The apparatus of claim 27, wherein said glucose detector is a reflectometer. 30. The apparatus of claim 22, wherein said vacuum is applied by a fixture having a major dimension ranging from about 2 mm to about 10 mm. 31. An assembly capable of providing an opening in skin of a patient by means of lancet, comprising: (a) a holder for holding a lancet assembly; (b) a means for providing sufficient force to cause said holder to be maintained in a position whereby a lancet in said holder would be positioned away from the skin of said patient; and (c) a means for allowing a gas to provide sufficient force to overcome the force provided by said holder maintaining means, whereby said gas causes said holder to be moved to a position whereby a lancet in said holder would be able to pierce the skin of said patient. 32. The assembly of claim 31 , further including a lancet assembly in said holder. 33. The assembly of claim 31 , wherein movement of said holder is brought about by means of said gas acting on a piston attached to said holder. 34. The assembly of claim 33, wherein said holder maintaining means (b) is a piston biasing means. 35. The assembly of claim 34, wherein said piston biasing means is a spring. 36. The assembly of claim 34, wherein said piston biasing means is a bellows. 37. The assembly of claim 31 , wherein said means (c) comprises a piston attached to said holder, said piston being disposed in a bore, said bore being capable of being opened to allow sufficient gas at sufficient pressure to enter to move said piston, whereby said holder is moved to said position whereby a lancet in said holder would be able to pierce the skin of said patient. 38. The assembly of claim 37, wherein said means (c) comprises a valve having a first port, a second port, and a third port, said first port capable of communicating with a source of gas at a first pressure, said second port capable of communicating with said bore, said third port capable of communicating with a source of gas at a second pressure, said second pressure being lower than said first pressure. 39. The assembly of claim 37, further including a means for sealing said bore. 40. The assembly of claim 39, wherein said sealing means is an o-ring. 41. The assembly of claim 39, wherein said sealing means is a bellows. 42. The assembly of claim 39, wherein said sealing means is a diaphragm. 43. The assembly of claim 31 , further including a piston, attached to said holder, which piston (1 ) travels in a first direction in a bore when gas at a first pressure enters said bore and said first pressure exceeds the pressure of gas in said bore prior to said entry of said gas at said first pressure and (2) travels in a second direction in said bore when said holder maintaining means (b) overcomes the force of gas acting on said piston in said bore. 44. An assembly capable of holding a lancet assembly for providing an opening in skin of a patient, comprising: (a) a housing having a bore having an axis; a valve fitted in a valve manifold; a first port in said valve manifold that allows said valve manifold to allow passage of gas at a first pressure through a first port in said valve; a second port in said valve manifold that allows said valve manifold to allow passage of said gas at said first pressure through a second port in said valve to enter said bore; a third port in said valve manifold that allows said valve manifold to allow passage of gas from said bore through a third port in said valve to a location having gas at a second pressure, said first pressure being greater than said second pressure; (b) a piston disposed in said bore, said piston having a proximal end and a distal end, said proximal end adjacent to said second port and said distal end including a holder for holding a lancet, said piston capable of moving along the axis of said bore; (c) means for biasing said piston so that said proximal end of said piston is in the furthest position away from the skin of said patient when said first port is closed. 45. The assembly of claim 44, wherein said piston biasing means (c) is a spring. 46. The assembly of claim 44, wherein said piston biasing means (c) is a bellows. 47. The assembly of claim 44, wherein said valve is actuated by a solenoid. 48. The assembly of claim 44, further including a means for sealing said bore. 49. The assembly of claim 48, wherein said means for sealing said bore is an o-ring. 50. The assembly of claim 48, wherein said means for sealing said bore is a bellows. 51 . The assembly of claim 48, wherein said means for sealing said bore is a diaphragm. 52. A method for forming an opening in skin of a patient in order to obtain blood, said method comprising the steps of: (1 ) providing a lancing assembly capable of providing an opening in skin of a patient by means of lancet, comprising: (a) a holder for holding a lancet assembly; (b) a means for providing sufficient force to cause said holder to be maintained in a position whereby a lancet in said holder would be positioned away from the skin of said patient; (c) a means for allowing a gas to provide sufficient force to overcome the force provided by said holder maintaining means, whereby said gas causes said holder to be moved to a position whereby a lancet in said holder would be able to pierce the skin of said patient; and (d) a lancing assembly in said holder, (2) positioning said lancing assembly sufficiently close to the skin of said patient so that a lancet in said lancet assembly can pierce the skin of said patient; (3) causing said means (c) to allow a gas to provide sufficient force to overcome the force provided by said holder maintaining means, so that said holder is moved to a position whereby said lancet in said lancet assembly pierces the skin of said patient. (4) causing said lancet to be retracted from the skin of said patient. 53. A multiple-layer element comprising: (a) a layer capable of receiving blood and transporting the blood received by means of chemically aided wicking; (b) a layer capable of detecting the presence of analyte or measuring the amount of analyte in blood; and (c) a layer that can be placed in contact with a meter, the meter- contactable layer overlying the blood-transporting layer, said layer (a) capable of transporting blood to said layer (b). 54. The article of claim 53, wherein said blood-transporting layer comprises a mesh. 55. The article of claim 53, wherein said blood-transporting layer comprises a surfactant. 56. The article of claim 53, wherein said blood-transporting layer has at least one opening therein. 57. The article of claim 53, wherein said analyte-detecting layer detects analyte by means of an electrical measurement. 58. The article of claim 53, wherein said analyte-detecting layer detects analyte by means of an optical measurement. 59. The article of claim 53, wherein no more than two microliters of blood are required for analyte determination. 60. The article of claim 53, wherein no more than one microliter of blood is required for analyte determination. 61. The article of claim 53, wherein an overcoat layer is coated about the periphery of said blood-transporting layer. 62. The article of claim 53, wherein said meter-contactable layer has at least one opening. 63. The article of claim 62, wherein said blood-transporting layer is at least partially superimposed over said at least one opening. 64. The article of claim 62 wherein said blood-transporting layer is not superimposed over said at least one opening. 65. The article of claim 62, wherein said meter-contactable layer has at least two openings. 66. A multiple-layer article comprising: (a) a covering layer having an opening therein; (b) a layer, overlying the covering layer, capable of receiving blood through the opening in the covering layer and transporting blood by means of chemically aided wicking; (c) a layer that can be placed in contact with a meter, the meter- contactable layer overlying the blood-transporting layer; and (d) a layer capable of detecting the presence of analyte or measuring the amount of analyte in blood, which layer is disposed between the covering layer and the meter-contactable layer and is capable of receiving blood from the blood-transporting layer. 67. The article of claim 66, wherein said blood-transporting layer is a mesh. 68. The article of claim 66, wherein said blood-transporting layer comprises a surfactant. 69. The article of claim 66, wherein said blood-transporting layer has at least one opening therein. 70. The article of claim 66, wherein said analyte-detecting layer detects analyte by means of an electrical measurement. 71. The article of claim 66, wherein said analyte-detecting layer detects analyte by means of an optical measurement. 72. The article of claim 66, wherein no more than two microliters of blood are required for analyte determination. 73. The article of claim 66, wherein no more than one microliter of blood is required for analyte determination. 74. The article of claim 66, wherein an overcoat layer is coated about the periphery of the blood-transporting layer 75. The article of claim 66, wherein said meter-contactable layer has at least one opening therein. 76. The article of claim 75, wherein said blood-transporting layer is at least partially superimposed over said at least one opening. 77. The article of claim 75, wherein said blood-transporting layer is not superimposed over said at least one opening. 78. The article of claim 75, wherein said meter-contactable layer has at least two openings therein. 79. A multiple-layer article comprising: (a) a covering layer; (b) a layer, overlying said covering layer, that can be placed in contact with a meter; and (c) a layer capable of detecting the presence of analyte or measures the amount of analyte in blood, which layer is disposed between said covering layer and said meter-contactable layer and is capable of receiving blood by means of capillary flow of blood between said covering layer and said meter- contactable layer, wherein said covering layer and said meter-contactable layer are spaced apart at a sufficient distance so that a capillary is formed between them. 80. The article of claim 79, wherein an overcoat layer spaces said covering layer and said meter-contactable layer at a sufficient distance so that a capillary is formed between said covering layer and said meter-contactable layer. 81. The article of claim 79, wherein said analyte-detecting layer detects analyte by means of an electrical measurement. 82. The article of claim 79, wherein said analyte-detecting layer detects analyte by means of an optical measurement. 83. The article of claim 79, wherein no more than two microliters of blood are required for analyte determination. 84 The article of claim 79, wherein no more than one microliter of blood is required for analyte determination. 85. The article of claim 79, wherein said meter-contactable layer has at least one opening therein 86. The article of claim 79, wherein said covering layer has an opening therein. 87. A method for performing a diagnostic test utilizing a sample of blood, said method comprising the steps of: (a) forming an unobstructed opening in an area of skin from which said sample is to be extracted; (b) extracting said sample from said unobstructed opening in said area of said skin, with the aid of vacuum and stretching of the skin; (c) providing a multiple-layer article comprising: (i) a layer capable of receiving blood and transporting the blood received by means of chemically aided wicking; (ii) a layer capable of detecting the presence of analyte or measuring the amount of analyte in blood; and (iii) a layer that can be placed in contact with a meter, the meter- contactable layer overlying the blood-transporting layer, said layer (i) capable of transporting blood to said layer (ii). (d) allowing said extracted sample to be received by said blood- transporting layer and allowing said blood to be transported by means of chemically aided wicking to said layer capable of detecting the presence of analyte or measuring the amount of analyte in blood; and (e) determining the presence of analyte or measuring the amount of analyte in blood. 88. The method of claim 87, wherein no more than two microliters of blood are required for analyte determination. 89. The method of claim 87, wherein no more than one microliter of blood is required for analyte determination. 90. A method for performing a diagnostic test utilizing a sample of blood, said method comprising the steps of: (a) forming an unobstructed opening in an area of skin from which said sample is to be extracted; (b) extracting said sample from said unobstructed opening in said area of said skin, with the aid of vacuum and stretching of the skin; (c) providing a multiple-layer article comprising: (i) a covering layer having an opening therein; (ii) a layer, overlying the covering layer, capable of receiving blood through the opening in the covering layer and transporting blood by means of chemically aided wicking; (iii) a layer that can be placed in contact with a meter, the meter- contactable layer overlying the blood-transporting layer; and (iv) a layer capable of detecting the presence of analyte or measuring the amount of analyte in blood, which layer is disposed between the covering layer and the meter-contactable layer and is capable of receiving blood from the blood-transporting layer. (d) allowing said extracted sample to be received by said blood- transporting layer and allowing said blood to be transported by means of chemically aided wicking to said layer capable of detecting the presence of analyte or measuring the amount of analyte in blood; and (e) determining the presence of analyte or measuring the amount of analyte in blood. 91. The method of claim 90, wherein no more than two microliters of blood are required for analyte determination. 92. The method of claim 90, wherein no more than one microliter of blood is required for analyte determination. 93. A method for performing a diagnostic test utilizing a sample of blood, said method comprising the steps of: (a) forming an unobstructed opening in an area of skin from which said sample is to be extracted; (b) extracting said sample from said unobstructed opening in said area of said skin, with the aid of vacuum and stretching of the skin; (c) providing a multiple-layer article comprising: (i) a covering layer; (ii) a layer, overlying said covering layer, that can be placed in contact with a meter; and (iii) a layer capable of detecting the presence of analyte or measures the amount of analyte in blood, which layer is disposed between said covering layer and said meter-contactable layer and is capable of receiving blood by means of capillary flow of blood between said covering layer and said meter-contactable layer, wherein said covering layer and said meter-contactable layer are spaced apart at a sufficient distance so that a capillary is formed between them; (d) allowing said extracted sample to be transported by means of capillary flow to said layer capable of detecting the presence of analyte or measuring the amount of analyte in blood; and (e) determining the presence of analyte or measuring the amount of analyte in blood. 94. The method of claim 93, wherein no more than two microliters of blood are required for analyte determination. 95. The method of claim 93, wherein no more than one microliter of blood is required for analyte determination. 96. A nosepiece suitable for use with a blood collection apparatus, said nosepiece comprising: (a) a lower base having an opening therein; (b) an upper base having an opening therein; and (c) an interior wall joining said upper base and said lower base, the area of said opening in said upper base being equal to or less than the area of said opening in said lower base. 97. The nosepiece of claim 96, further including at least one passageway for vacuum. 98. The nosepiece of claim 96, wherein said opening in said upper base is circular in shape. 99. The nosepiece of claim 96, wherein said opening in said upper base is oval in shape. 100. The nosepiece of claim 96, wherein said interior wall is tapered. 101. The nosepiece of claim 96, wherein said interior wall is comprised of stepwise cylindrical sections. 102. The nosepiece of claim 96, wherein said opening in said upper base is surrounded by a rim. 103. The nosepiece of claim 96, further including a seal attached to said lower base of said nosepiece. 104. The nosepiece of claim 103, wherein said seal is in the form of an annular ring. 105. The nosepiece of claim 103, wherein said seal is capable of moving between a first position and a second position. 106. The nosepiece of claim 103, wherein said seal is formed from rubber or an elastomeric material. 107. The nosepiece of claim 103, wherein said seal is formed from an adhesive. 108. An apparatus suitable for obtaining a sample of blood for analysis in a diagnostic test, comprising: (a) a housing having a sealable chamber located therein and a sealable opening in fluid communication with said sealable chamber, (b) a power source, (c) a vacuum pump operably connected to said power source, said vacuum pump in communication with said sealable chamber, (d) a lancing assembly positioned in said housing, said lancing assembly capable of moving a lancet towards said sealable opening, and (e) a fluid collector positioned in said sealable chamber, said fluid collector in fluid communication with said sealable opening. 109. The apparatus of claim 108, wherein said housing comprises: (a) a body portion, and (b) a door portion, said door portion positionable over said body portion and including said sealable opening. 1 10. The apparatus of claim 109, wherein said fluid collector is positioned in a slot in said door portion. 1 11. The apparatus of claim 110, wherein said slot locates said fluid collector adjacent said sealable opening when said door portion is positioned over said body portion. 112. The apparatus of claim 109, wherein said body portion contains at least one slot for inserting said fluid collector. 1 13. The apparatus of claim 109, wherein said body portion includes at least one electrical connection. 1 14. The apparatus of claim 109, wherein said door portion includes at least one electrical connection. 115. The apparatus of claim 109, wherein said body portion comprises a movable projection containing a slot, said fluid collector positioned in said slot. 1 16. The apparatus of claim 115, wherein said movable projection includes at least one electrical connection. 1 17. The apparatus of claim 108, wherein said housing comprises: (a) a body portion, (b) an interior cover portion positionable over said lancing assembly, and (c) a door portion positionable over said interior cover portion and including said sealable opening. 1 18. The apparatus of claim 117, wherein said interior cover portion contains at least one alignment channel to position said fluid collector. 119. The apparatus of claim 117, wherein said door portion contains at least one alignment fixture to position said fluid collector. 120. The apparatus of claim 117, wherein the housing further comprises a projection. 121. The apparatus of claim 120, wherein said fluid collector is positioned in at least one slot in said projection. 122. The apparatus of claim 121 , wherein said at least one slot is parallel to the upper surface of said interior cover. 123. The apparatus of claim 121 , wherein said at least one slot is not parallel to the upper surface of said interior cover. 124. The apparatus of claim 121 , wherein said projection includes at least one electrical connection. 125. The apparatus of claim 108, further comprising a heating element. 126. The apparatus of claim 108, wherein said fluid collector comprises a biosensor. 127. The apparatus of claim 126, wherein said biosensor comprises a glucose detector. 128. The apparatus of claim 108 wherein said fluid collector comprises a reflectance strip. 129. The apparatus of claim 128, wherein said reflectance strip comprises a glucose detector. 130. The apparatus of claim 108, further comprising a reflectometer. 131. The apparatus of claim 108, further comprising a display operably connected to said power source and said fluid collector. 132. The apparatus of claim 108, further comprising a switch operably connected to said vacuum pump and said lancing assembly through said power source. 133. The apparatus of claim 108, further comprising electronics. 134. The apparatus of claim 133, wherein the electronics control power to said vacuum pump. 135. The apparatus of claim 133, wherein the electronics control power to a heating element. 136. The apparatus of claim 133, wherein the electronics control power to the lancing assembly. 137. The apparatus of claim 108, further comprising more than one of said fluid collector. 138. A method for obtaining a sample of blood for a diagnostic test, said method comprising the steps of: (a) placing a blood collection device over a region on the surface of the skin from which said sample is to be obtained, (b) forming a seal between said blood collection device and said surface of the skin, (c) creating a vacuum sufficient to result in said surface of the skin becoming stretched and engorged with blood, (d) triggering a lancing assembly and causing a lancet to penetrate said skin, (e) retracting said lancet, (f) withdrawing blood toward and onto a fluid collector, and (g) releasing the vacuum. 139. The method of claim 138, further comprising the step of generating a signal indicative of glucose level. 140. The method of claim 138, further comprising the step of causing said fluid collector to move to a position near the position where said lancet penetrated said skin. 141. The method of claim 140, wherein said movement of the fluid collector is created by the release of a latch. 142. The method of claim 140, wherein said movement of the fluid collector is created by a four-bar linkage. 143. The method of claim 140, wherein said movement of the fluid collector is created by a pivoting projection.

Inventors: CHAMBERS GEOFFREY R, CUNNINGHAM DAVID D, GOLDFARB JOSHUA P, GRAHAM HUGH W, HENNING TIMOTHY P, HUGHES GRAHAM J, LOWERY MICHAEL G, MUETTERTIES ANDREW J, PROKOP GARY F, SCHAPIRA THOMAS G, SHAIN ERIC B, WATKIN JARED L, YOUNG DOUGLAS F, CHAMBERS, GEOFFREY, R., CUNNINGHAM, DAVID, D., GOLDFARB, JOSHUA, P., GRAHAM, HUGH, W., HENNING, TIMOTHY, P., HUGHES, GRAHAM, J., LOWERY, MICHAEL, G., MUETTERTIES, ANDREW, J., PROKOP, GARY, F., SCHAPIRA, THOMAS, G., SHAIN, ERIC, B., WATKIN, JARED, L., YOUNG, DOUGLAS, F.
Applicants: ABBOTT LAB, CHAMBERS GEOFFREY R, CUNNINGHAM DAVID D, GOLDFARB JOSHUA P, GRAHAM HUGH W, HENNING TIMOTHY P, HUGHES GRAHAM J, LOWERY MICHAEL G, MUETTERTIES ANDREW J, PROKOP GARY F, SCHAPIRA THOMAS G, SHAIN ERIC B, WATKIN JARED L, YOUNG DOUGLAS F, ABBOTT LABORATORIES, CHAMBERS, GEOFFREY, R., CUNNINGHAM, DAVID, D., GOLDFARB, JOSHUA, P., GRAHAM, HUGH, W., HENNING, TIMOTHY, P., HUGHES, GRAHAM, J., LOWERY, MICHAEL, G., MUETTERTIES, ANDREW, J., PROKOP, GARY, F., SCHAPIRA, THOMAS, G., SHAIN, ERIC, B., WATKIN, JARED, L., YOUNG, DOUGLAS, F.
Application year: 1997
Main classification: A61B5
IPC codes: A61B5, G01N33