Abstract:
A mixing apparatus for mixing a first component and a second component comprises: a first vessel which has a negative internal pressure and houses the first component; a second vessel which houses the second component; and a double-ended needle which allows communication between the first vessel and the second vessel when a first stopper element and a second stopper element have been pierced through by the needle. Penetration-resistance increasing parts which have a greater penetration resistance with respect to the first stopper element and the second stopper element than tip end tubes are respectively provided on a first puncture needle and a second puncture needle of the double-ended needle at positions further towards the base end than the tip end tubes. The axial heights of the edge faces of the tip end tubes are both less than the thicknesses of the first stopper element and of the second stopper element.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a mixing instrument (apparatus) for mixing a first component in a solid phase or a liquid phase and a second component in a liquid phase with each other. The present invention also relates to a piercing method for a double-ended needle. 
       BACKGROUND ART 
       [0002]    Heretofore, in a medical organization or the like, when a patient is to be given an intravenous drip injection (for transfusion), an adhesion preventive, or a living tissue adhesive or the like, it often is customary to prepare a drug solution by diluting or dissolving a drug within a liquid, and then to draw the drug solution into a syringe. To produce such a drug solution, a device with a double-ended needle is used. More specifically, a plug (rubber plug) on a drug container which contains a drug in a solid phase or a liquid phase, and which has a negative pressure developed therein, is pierced with one end of the double-ended needle to connect the drug container to the double-ended needle, and a plug on a liquid container, which contains a liquid such as distilled water or the like, is pierced with the other end of the double-ended needle to connect the liquid container to the double-ended needle, thereby bringing the drug container and the liquid container into fluid communication with each other through the double-ended needle. Since a negative pressure is developed in the drug container, the liquid in the liquid container is attracted to and flows into the drug container via the double-ended needle. Thereafter, the drug container is shaken several times. The drug in the drug container becomes diluted and is dissolved by the liquid that has flowed into the drug container. 
         [0003]    Background art, which is concerned with a device for mixing a drug and a liquid using a double-ended needle, is disclosed in Japanese Laid-Open Patent Publication No. 2008-523851 (PCT) and Japanese Laid-Open Patent Publication No. 2001-333961, for example. 
       SUMMARY OF INVENTION 
       [0004]    When the double-ended needle is connected to the drug container and the liquid container, if the piercing point of the double-ended needle for the drug container is inserted through the plug on the drug container before the piercing point of the double-ended needle for the liquid container is inserted through the plug on the liquid container, then the negative pressure in the drug container is eliminated, making it impossible to attract the liquid from the liquid container. Conversely, if the piercing point of the double-ended needle for the liquid container is inserted through the plug on the liquid container before the piercing point of the double-ended needle for the drug container is inserted through the plug on the drug container, then the liquid tends to unduly leak from the liquid container. Consequently, the amount of liquid that flows into the drug container tends to change, and a proper amount of liquid to be mixed with the drug cannot be made available. 
         [0005]    Therefore, the mixing instruments according to the background art are liable to cause a handling error by eliminating the negative pressure in the drug container or by allowing liquid to leak from the liquid container, unless the timing at which the piercing point of the double-ended needle for the drug container is inserted through the plug on the drug container is the same as the timing at which the piercing point of the double-ended needle for the liquid container is inserted through the plug on the liquid container. The above two timings may be brought into conformity with each other by increasing the speed at which the double-ended needle is inserted into the drug container and the liquid container. However, such an approach is difficult to apply if the double-ended needle is handled by persons who are not sufficiently skilled or physically strong enough. 
         [0006]    The present invention has been made in view of the above problems. It is an object of the present invention to provide a mixing instrument, which can be handled easily without causing handling errors, by maintaining a negative pressure in a drug container and preventing liquid from leaking from a liquid container, even if the timing at which a puncture needle for the drug container of a double-ended needle penetrates a plug on the drug container differs from the timing at which a puncture needle for the liquid container of the double-ended needle penetrates a plug on the liquid container. Another object of the present invention is to provide a piercing method for a double-ended needle. 
         [0007]    To achieve the above objects, there is provided in accordance with the present invention a mixing instrument for mixing a first component and a second component with each other, comprising a first container for storing the first component, the first container having a mouth sealed by a first plug made of an elastic material and having a negative pressure developed therein, a second container for storing the second component, the second container having a mouth sealed by a second plug made of an elastic material, and a double-ended needle having a first puncture needle for piercing the first plug and a second puncture needle for piercing the second plug, wherein the double-ended needle brings the first container and the second container into fluid communication with each other when the first puncture needle pierces the first plug and the second puncture needle pierces the second plug, wherein the first puncture needle and the second puncture needle include respective increased penetration resistance members disposed at positions closer to proximal end portions than distal-end tubes thereof including cutting faces, and having a greater penetration resistance to the first plug and the second plug than the distal-end tubes, and wherein the cutting faces of the distal-end tubes have respective heights in an axial direction which are smaller than thicknesses of the first plug and the second plug. 
         [0008]    With the above arrangement of the present invention, the first puncture needle and the second puncture needle have respective distal-end tubes with openings formed in the cutting faces on distal ends thereof, and the respective increased penetration resistance members, which are disposed at positions closer to the proximal end portions than the distal-end tubes thereof, and having a greater penetration resistance to the first plug and the second plugs than the distal-end tubes. When the double-ended needle is connected to the first container and the second container, the distal-end tubes, including needle points with a relatively small penetration resistance, are initially inserted into the rubber plugs, and then, the increased penetration resistance members with a relatively large penetration resistance are inserted into the rubber plugs. After the openings in the needle points of the first puncture needle and the second puncture needle have been closed respectively by the first plug and the second plug, the first puncture needle and the second puncture needle penetrate the first plug and the second plug, respectively. Consequently, the negative pressure in the drug container is maintained and liquid is prevented from leaking out, even if the timing at which the first puncture needle penetrates the first plug differs from the timing at which the second puncture needle penetrates the second plug. More specifically, even if the first puncture needle penetrates the first plug before the second puncture needle penetrates the second plug, since the opening in the distal end of the second puncture needle is closed by the second plug, the negative pressure in the drug container is maintained. Further, even if the second puncture needle penetrates the second plug before the first puncture needle penetrates the first plug, since the opening in the distal end of the first puncture needle is closed by the first plug, liquid is prevented from leaking out. According to the present invention, since the negative pressure in the first container is maintained and liquid is prevented from leaking out, even if the timing at which the first puncture needle penetrates the first plug differs from the timing at which the second puncture needle penetrates the second plug, a mixing instrument is provided which can be handled easily without causing handling errors. 
         [0009]    In the above mixing instrument, the increased penetration resistance members comprise increased diameter members having outside diameters greater than the outside diameters of the distal-end tubes. 
         [0010]    With the above arrangement, since the increased penetration resistance members comprise the increased diameter members, respectively, having an outside diameter greater than the outside diameter of the distal-end tubes, the penetration resistance is increased with a simple arrangement by a step provided by the different outside diameters of the distal-end tubes and the increased diameter members. 
         [0011]    In the above mixing instrument, the first puncture needle and the second puncture needle have respective inner tubes made of metal and including the distal-end tubes and respective outer tubes surrounding the inner tubes that serve as the increased penetration resistance members. 
         [0012]    With the above arrangement, since the distal-end tubes including the cutting edges are made of metal, the cutting edges can easily be formed as sharp edges. The cutting edges, which are formed as sharp edges, reduce the penetration resistance of the distal-end tubes with respect to the first plug and the second plug, thereby reducing the forces required to cause the distal-end tubes to pierce the first plug and the second plug. The mixing instrument can thus be handled more easily. 
         [0013]    The above mixing instrument further comprises a first holder shaped as a hollow tube having a first opening formed in an end thereof, the first container being mounted in the first holder, a second holder shaped as a hollow tube having a second opening formed in an end thereof, the second container being mounted in the second holder, and a connector, the double-ended needle being mounted on the connector, the connector being slidable in an axial direction of the double-ended needle into fitting engagement with the end of the first holder with the first container insertion opening formed therein, and being slidable in an axial direction of the double-ended needle into fitting engagement with the end of the second holder with the second container insertion opening formed therein. 
         [0014]    With the above arrangement, the first holder with the first container mounted therein and with the first plug positioned near the first opening, and the connector with the first puncture needle oriented toward the first plug are slid axially into fitting engagement with each other. Further, the second holder with the second container mounted therein and with the second plug positioned near the second opening, and the connector with the second puncture needle oriented toward the second plug are slid axially into fitting engagement with each other. The first puncture needle thus pierces the first plug, while the second puncture needle pierces the second plug. When the first holder, the connector, and the second holder are fitted together, they slide against each other and are guided in relative axial movement. Therefore, the first puncture needle and the second puncture needle can pierce the first plug and the second plug, respectively, accurately and simply in the axial direction, whereby the mixing instrument can be handled more easily. 
         [0015]    The above mixing instrument further comprises a lock mechanism for releasably locking the first holder, the connector, and the second holder inseparably together when the first holder, the connector, and the second holder are fitted together in a relative positional relation, such that the first puncture needle pierces the first plug and the second puncture needle pierces the second plug. 
         [0016]    With the above arrangement, when the first holder, the connector, and the second holder are coupled together, they are locked by the lock mechanism so that they can be handled in their entirety as an integrated mixing instrument. Consequently, it is easy to perform the process of shaking the mixing instrument in order to accelerate mixing of the first component and the second component. 
         [0017]    In the above mixing instrument, the first container, the second container, and the double-ended needle each are provided in two sets, two first containers are mounted in the first holder, two second containers are mounted in the second holder, paired double-ended needles are mounted on the connector and spaced from each other in directions perpendicular to the axial direction, and one of the double-ended needles and the other double-ended needle have respective cutting faces facing away from each other in directions in which the double-ended needles are spaced from each other. 
         [0018]    With the above arrangement, when the paired double-ended needles pierce the first plug and the second plug, respectively, forces acting horizontally on the double-ended needles cancel each other out. Therefore, the sliding resistance between the first holder, the connector, and the second holder is prevented from increasing when such elements are fitted together. Since resistive forces are prevented from unduly increasing at the time that the first holder, the connector, and the second holder are coupled together, the mixing instrument can be handled with greater ease. 
         [0019]    According to the present invention, there also is provided a piercing method for causing a double-ended needle, having a first puncture needle on one end and a second puncture needle on another end thereof, to pierce a first plug made of an elastic material and sealing a mouth of a first container and a second plug made of an elastic material and sealing a mouth of a second container having a negative pressure developed therein, thereby bringing the first container and the second container into fluid communication with each other, comprising the steps of preparing the double-ended needle having the first puncture needle and the second puncture needle which include respective increased penetration resistance members disposed at positions closer to proximal end portions than distal-end tubes thereof including cutting faces, and having a greater penetration resistance to the first plug and the second plug than the distal-end tubes, sealing both ends by pressing a distal end of the first puncture needle into the first plug to close a first opening formed in the distal end of the first puncture needle with the first plug while temporarily preventing a distance by which the first puncture needle is inserted into the first plug from increasing with the increased penetration resistance member of the first puncture needle, and pressing a distal end of the second puncture needle into the second plug to close a second opening formed in the distal end of the second puncture needle while temporarily preventing a distance by which the second puncture needle is inserted into the second plug from increasing with the increased penetration resistance member of the second puncture needle, and after sealing both ends, piercing the first plug with the first puncture needle and piercing the second plug with the second puncture needle to thereby bring the first container and the second container into fluid communication with each other. 
         [0020]    With the above piercing method for the double-ended needle according to the present invention, the negative pressure in the drug container is maintained and the liquid is prevented from leaking out, even if the timing at which the first puncture needle penetrates the first plug differs from the timing at which the second puncture needle penetrates the second plug. More specifically, even if the first puncture needle penetrates the first plug before the second puncture needle penetrates the second plug, since the opening in the distal end of the second puncture needle is closed by the second plug, negative pressure in the drug container is maintained. Further, even if the second puncture needle penetrates the second plug before the first puncture needle penetrates the first plug, since the opening in the distal end of the first puncture needle is closed by the first plug, liquid is prevented from leaking out. According to the present invention, therefore, the plugs can be pierced by the double-ended needle simply without handling errors, by maintaining the negative pressure in the first container and preventing liquid from leaking out, even if the timing at which the first puncture needle penetrates the first plug differs from the timing at which the second puncture needle penetrates the second plug. 
         [0021]    According to the present invention, there also is provided a mixing instrument for mixing a first component and a second component with each other, comprising a first container for storing the first component, the first container being sealed by a first plug made of an elastic material and having a negative pressure developed therein, a second container for storing the second component, the second container having a mouth sealed by a second plug made of an elastic material, and a double-ended needle having a first puncture needle for piercing the first plug and a second puncture needle for piercing the second plug, wherein the double-ended needle brings the first container and the second container into fluid communication with each other when the first puncture needle pierces the first plug and the second puncture needle pierces the second plug, wherein respective needle point angles of the first puncture needle and the second puncture needle and respective elastic characteristics of the first plug and the second plug are established, such that when the first puncture needle is pressed by the first plug and the second puncture needle is pressed by the second plug, openings formed in opposite ends of a lumen of the double-ended needle are sealed by the first plug and the second plug, respectively, and wherein the first puncture needle and the second puncture needle have respective cutting faces having respective heights in an axial direction which are smaller than thicknesses of the first plug and the second plug. 
         [0022]    With the above arrangement according to the present invention, since the needle point angles of the first puncture needle and the second puncture needle and the elastic characteristics of the first plug and the second plug are established in the foregoing manner, when the double-ended needle pierces the first plug and the second plug, the first plug pressed by the first puncture needle and the second plug pressed by the second puncture needle are initially elastically deformed, and openings in opposite ends of the lumen are simultaneously sealed before the first puncture needle and the second puncture needle penetrate through the first plug and the second plug, respectively. Therefore, even if the timing at which the first puncture needle penetrates the first plug differs from the timing at which the second puncture needle penetrates the second plug, negative pressure in the drug container is maintained and liquid is prevented from leaking out. More specifically, even if the first puncture needle penetrates the first plug before the second puncture needle penetrates the second plug, since the opening of the lumen of the second puncture needle is sealed by the second plug, negative pressure in the drug container is maintained. Further, even if the second puncture needle penetrates the second plug before the first puncture needle penetrates the first plug, since the opening of the lumen of the first puncture needle is sealed by the first plug, liquid is prevented from leaking out. According to the present invention, therefore, even if the timing at which the first puncture needle penetrates the first plug of the drug container differs from the timing at which the second puncture needle penetrates the second plug of the liquid container, negative pressure in the drug container is maintained and liquid is prevented from leaking out. Accordingly, a mixing instrument is provided, which can be handled easily without causing handling errors. 
         [0023]    In the above mixing instrument, the cutting faces of the first puncture needle and the second puncture needle are shaped as concave surfaces, which are curved as viewed in vertical cross section, and a point of intersection between a line segment that extends between a proximal end portion of each of the cutting faces and a distal end portion thereof, and a line normal to the line segment that extends from a deepest point on the concave surface is positioned closer to the proximal end portion of the cutting face than the midpoint of the line segment, and a center of the lumen is closer to the proximal end portion of the cutting face than a central line of each puncture needle. 
         [0024]    With the above arrangement, the proximal end areas of the cutting faces, which are formed as concave surfaces, of the first puncture needle and the second puncture needle function as chins. Since such chins increase the penetration resistance by which the first plug and the second plug are penetrated, when the distal ends of the first puncture needle and the second puncture needle bite into the first plug and the second plug, the chins temporarily bear the first plug and the second plug. Since the openings of the lumen are positioned closer to the proximal end portions (the chins) of the cutting faces than the central line of the needle, while the chins bear the first plug and the second plug, the openings in opposite ends of the lumen are simultaneously sealed by the first plug and the second plug. 
         [0025]    The above mixing instrument further comprises a first holder shaped as a hollow tube having a first opening formed in one end thereof, the first container being mounted in the first holder, a second holder shaped as a hollow tube having a second opening formed in one end thereof, the second container being mounted in the second holder, and a connector, the double-ended needle being mounted on the connector, the connector being slidable in an axial direction of the double-ended needle into fitting engagement with the end of the first holder with the first container insertion opening formed therein, and being slidable in an axial direction of the double-ended needle into fitting engagement with the end of the second holder with the second container insertion opening formed therein. 
         [0026]    With the above arrangement, the first holder with the first container mounted therein and with the first plug positioned near the first opening, and the connector with the first puncture needle oriented toward the first plug are slid axially into fitting engagement with each other. Also, the second holder with the second container mounted therein and with the second plug positioned near the second opening, and the connector with the second puncture needle oriented toward the second plug are slid axially into fitting engagement with each other. Therefore, the first puncture needle pierces the first plug and the second puncture needle pierces the second plug. When the first holder, the connector, and the second holder are fitted together, such elements slide against each other and are guided for relative axial movement. Therefore, the first puncture needle and the second puncture needle can pierce the first plug and the second plug, respectively, accurately and simply in the axial direction. Consequently, the mixing instrument can be handled more easily. 
         [0027]    The above mixing instrument further comprises a lock mechanism for releasably locking the first holder, the connector, and the second holder inseparably together when the first holder, the connector, and the second holder are fitted together in a relative positional relation, such that the first puncture needle pierces the first plug and the second puncture needle pierces the second plug. 
         [0028]    With the above arrangement, when the first holder, the connector, and the second holder are coupled together, the components are locked by the lock mechanism so that they can be handled in their entirety as an integrated mixing instrument. Consequently, it is easy to perform the process of shaking the mixing instrument to accelerate mixing of the first component and the second component. 
         [0029]    In the above mixing instrument, the first container, the second container, and the double-ended needle each are provided in two sets, such that two first containers are mounted in the first holder, two second containers are mounted in the second holder, the paired puncture needles are mounted on the connector and spaced from each other in directions perpendicular to the axial direction, and one of the double-ended needles and the other double-ended needle have respective cutting faces facing away from each other in directions in which the double-ended needles are spaced from each other. 
         [0030]    With the above arrangement, when the paired double-ended needles pierce the first plug and the second plug, respectively, horizontal forces acting on the double-ended needles cancel each other out. Therefore, sliding resistance between the first holder, the connector, and the second holder is prevented from increasing when the components are fitted together. Since resistive forces are prevented from unduly increasing at the time that the first holder, the connector, and the second holder are coupled together, the mixing instrument can be handled with greater ease. 
         [0031]    According to the present invention, there is further provided a piercing method for causing a double-ended needle, having a first puncture needle on one end and a second puncture needle on another end thereof, to pierce a first plug made of an elastic material and sealing a mouth of a first container, and a second plug made of an elastic material and sealing a mouth of a second container having a negative pressure developed therein, thereby bringing the first container and the second container into fluid communication with each other. The method comprises the steps of preparing the double-ended needle, the first plug, and the second plug, wherein respective needle point angles of the first puncture needle and the second puncture needle and respective elastic characteristics of the first plug and the second plug are established, such that when the first puncture needle is pressed by the first plug and the second puncture needle is pressed by the second plug, openings formed in opposite ends of a lumen of the double-ended needle are sealed by the first plug and the second plug, respectively, sealing both ends by pressing a distal end of the first puncture needle into the first plug to elastically deform the first plug and to close a first opening formed in the distal end of the first puncture needle with the first plug, and pressing a distal end of the second puncture needle into the second plug to elastically deform the second plug and to close a second opening formed in the distal end of the second puncture needle with the second plug, and after sealing both ends, piercing the first plug with the first puncture needle and piercing the second plug with the second puncture needle to thereby bring the first container and the second container into fluid communication with each other. 
         [0032]    With the above piercing method for a double-ended needle according to the present invention, the negative pressure in the drug container is maintained and the liquid is prevented from leaking out, even if the timing at which the first puncture needle penetrates the first plug differs from the timing at which the second puncture needle penetrates the second plug. More specifically, even if the first puncture needle penetrates the first plug before the second puncture needle penetrates the second plug, since the opening in the distal end of the second puncture needle is closed by the second plug, negative pressure in the drug container is maintained. Further, even if the second puncture needle penetrates the second plug before the first puncture needle penetrates the first plug, since the opening in the distal end of the first puncture needle is closed by the first plug, liquid is prevented from leaking out. According to the present invention, therefore, the plugs can be pierced by the double-ended needle simply and without handling errors by maintaining the negative pressure in the first container and preventing the liquid from leaking out, even if the timing at which the first puncture needle penetrates the first plug differs from the timing at which the second puncture needle penetrates the second plug. 
         [0033]    According to the present invention, the mixing instrument can be handled easily without causing handling errors by maintaining the negative pressure in the drug container and by preventing liquid from leaking out, even if the timing at which the puncture needle for the drug container of the double-ended needle penetrates the plug on the drug container differs from the timing at which the puncture needle for the liquid container of the double-ended needle penetrates the plug on the liquid container. 
         [0034]    According to the present invention, the piercing method for the double-ended needle allows the double-ended needle to pierce the plugs simply without causing handling errors. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0035]      FIG. 1  is a cross-sectional view of a mixing instrument according to a first embodiment of the present invention; 
           [0036]      FIG. 2A  is an enlarged cross-sectional view, partially omitted from illustration, showing a lock mechanism in a first state; 
           [0037]      FIG. 2B  is an enlarged cross-sectional view, partially omitted from illustration, showing the lock mechanism in a second state; 
           [0038]      FIG. 3  is an enlarged cross-sectional view, partially omitted from illustration, showing a double-ended needle and nearby parts of the mixing instrument according to the first embodiment of the present invention; 
           [0039]      FIG. 4  is an enlarged cross-sectional view, partially omitted from illustration, illustrative of dimensions of a distal end portion of the double-ended needle of the mixing instrument according to the first embodiment of the present invention; 
           [0040]      FIG. 5  is a cross-sectional view showing the manner in which the double-ended needle of the mixing instrument according to the first embodiment of the present invention has distal-end tubes thereof inserted into a first plug and a second plug; 
           [0041]      FIG. 6  is an enlarged cross-sectional view, partially omitted from illustration, showing the manner in which the double-ended needle of the mixing instrument according to the first embodiment of the present invention has one of the distal-end tubes thereof inserted into the first plug; 
           [0042]      FIG. 7  is a cross-sectional view showing the manner in which the double-ended needle of the mixing instrument according to the first embodiment of the present invention extends through the first plug and the second plug, thereby bringing a first container and a second container into fluid communication with each other; 
           [0043]      FIG. 8A  is an enlarged cross-sectional view, partially omitted from illustration, showing a first modification of the double-ended needle of the mixing instrument according to the first embodiment of the present invention; 
           [0044]      FIG. 8B  is an enlarged cross-sectional view, partially omitted from illustration, showing a second modification of the double-ended needle of the mixing instrument according to the first embodiment of the present invention; 
           [0045]      FIG. 9  is an exploded perspective view of a mixing instrument according to a second embodiment of the present invention; 
           [0046]      FIG. 10  is a cross-sectional view of the mixing instrument according to the second embodiment of the present invention; 
           [0047]      FIG. 11  is a cross-sectional view showing the manner in which double-ended needles of the mixing instrument according to the second embodiment of the present invention have distal-end tubes thereof inserted into first plugs and second plugs; 
           [0048]      FIG. 12  is a cross-sectional view showing the manner in which the double-ended needles of the mixing instrument according to the second embodiment of the present invention extend through the first plugs and the second plugs, thereby bringing first containers and second containers into fluid communication with each other; 
           [0049]      FIG. 13  is a cross-sectional view of a mixing instrument according to a third embodiment of the present invention; 
           [0050]      FIG. 14  is an enlarged cross-sectional view, partially omitted from illustration, showing a double-ended needle and nearby parts of the mixing instrument according to the third embodiment of the present invention; 
           [0051]      FIG. 15  is an enlarged cross-sectional view, partially omitted from illustration, showing a first puncture needle and nearby parts of the mixing instrument according to the third embodiment of the present invention; 
           [0052]      FIG. 16  is a cross-sectional view showing the manner in which the double-ended needle of the mixing instrument according to the third embodiment of the present invention pierces a first plug and a second plug; 
           [0053]      FIG. 17  is an enlarged cross-sectional view, partially omitted from illustration, showing the manner in which a lumen of the first puncture needle of the mixing instrument according to the third embodiment of the present invention is sealed by the first plug; 
           [0054]      FIG. 18  is a cross-sectional view showing the manner in which the double-ended needle of the mixing instrument according to the third embodiment of the present invention extends through the first plug and the second plug, thereby bringing a first container and a second container into fluid communication with each other; 
           [0055]      FIG. 19  is an exploded perspective view of a mixing instrument according to a fourth embodiment of the present invention; 
           [0056]      FIG. 20  is a cross-sectional view of the mixing instrument according to the fourth embodiment of the present invention; 
           [0057]      FIG. 21  is an enlarged cross-sectional view, partially omitted from illustration, showing a pair of double-ended needles and nearby parts of the mixing instrument according to the fourth embodiment of the present invention; 
           [0058]      FIG. 22  is a cross-sectional view showing the manner in which the double-ended needles of the mixing instrument according to the fourth embodiment of the present invention pierce first plugs and second plugs; and 
           [0059]      FIG. 23  is a cross-sectional view showing the manner in which the double-ended needles of the mixing instrument according to the fourth embodiment of the present invention extend through the first plugs and the second plugs, thereby bringing first containers and second containers into fluid communication with each other. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0060]    Embodiments of the present invention will hereinafter be described below with reference to the drawings. For illustrative purposes, the upper side, the lower side, the left side, and the right side in  FIGS. 1 to 12  will be referred to as “upper,” “lower,” “left,” and “right” sides respectively. 
       First Embodiment 
       [0061]      FIG. 1  is a cross-sectional view of a mixing instrument  10  according to a first embodiment of the present invention. The mixing instrument  10  serves to mix a first component in a solid phase or a liquid phase, and a second component in a liquid phase. Although the first component is illustrated as being in a solid phase or a liquid phase, whereas the second component is illustrated as being in a liquid phase, the components are not limited to such states. The first component may be in a gel state or a gaseous state. Similarly, the second component may be in a gel state or a gaseous state. 
         [0062]    As shown in  FIG. 1 , the mixing instrument  10  includes a drug container (first container)  12  for storing the first component therein, a drug holder (first holder)  14  for mounting the drug container  12  thereon, a liquid container (second container)  16  for storing the second component therein, a liquid holder (second holder)  18  for mounting the liquid container  16  thereon, a double-ended needle  20  for bringing the drug container  12  and the liquid container  16  into fluid communication with each other, and a connector  22  to which the double-ended needle  20  is fixed. 
         [0063]    The drug container  12  and the liquid container  16  are not limited to any particular type of container, but may be vials or the like. 
         [0064]    The drug container  12  stores a drug as the first component. The drug is not limited to any particular form, but may be a solid (tablets, granules, etc.), a powder (powder medicine, etc.), or a liquid (liquid medicine, etc.). If a living tissue adhesive is to be prepared, then the drug may be thrombin or fibrinogen. If an adhesion preventive is to be prepared, then the drug may be carboxymethyl dextrin produced by modifying a drug with a succinimidyl group, for example, or a mixture of sodium hydrogen carbonate and sodium carbonate. The drug container  12  has a negative pressure developed therein. 
         [0065]    The liquid container  16  stores a liquid as the second component. The second component is a liquid such as distilled water or the like, for example, which dilutes or dissolve the drug that makes up the second component. 
         [0066]    As shown in  FIG. 1 , the drug container  12  includes a hard container body  24  and a first plug  26  made of an elastic material, which hermetically seals the mouth of the container body  24 . The liquid container  16  includes a hard container body  28  and a second plug  30  made of an elastic material, which hermetically seals the mouth of the container body  28 . 
         [0067]    The container bodies  24 ,  28  are made of a material, which is not limited to any particular material, but which may be any of various glasses or various resins, such as polyvinyl chloride, polyethylene, polypropylene, cyclic polyolefin, polystyrene, poly-(4-methylpentene-1), polycarbonate, acrylic resin, an acrylonitrile-butadiene-styrene copolymer, a polyester such as polyethylene terephthalate, polyethylene naphthalate, or the like, a butadiene-styrene copolymer, and polyamide (e.g., nylon 6, nylon 6·6, nylon 6·10, or nylon 12). Resins are preferable to glasses. If the container bodies  24 ,  28  are made of a resin, then the container bodies  24 ,  28  can be discarded by burning and hence the process of discarding the container bodies  24 ,  28  can be minimized. The container bodies  24 ,  28  should preferably be permeable to light (virtually transparent or translucent) for keeping the interior thereof visible. 
         [0068]    The first plug  26  and the second plug  30  can be pierced by a first puncture needle  42  and a second puncture needle  44 , to be described later. The first plug  26  and the second plug  30  are made of a material, which is not limited to any particular material, but which may be any of various rubber materials, such as natural rubber, butyl rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, and silicone rubber, various thermoplastic elastomers such as a polyurethane thermoplastic elastomer, a polyester thermoplastic elastomer, a polyamide thermoplastic elastomer, an olefin thermoplastic elastomer, and a styrene thermoplastic elastomer, and elastic materials including mixtures of the aforementioned materials. If the first plug  26  and the second plug  30  are made of butyl rubber, then the rubber hardness thereof should preferably have a Shore A hardness in the range from 39 to 53°, and more preferably, in the range from 45 to 47°. 
         [0069]    Portions of the first plug  26  and the second plug  30 , which are pierced by the double-ended needle  20 , have a thickness t (see  FIG. 5 ), which preferably is in the range from 1 to 4 mm, and more preferably, in the range from 2.0 to 2.5 mm. 
         [0070]    The drug holder  14  is a bottomed tubular component for storing the drug container  12  therein. The drug holder  14  is made of any of various resins, such as polyvinyl chloride, polyethylene, polypropylene, cyclic polyolefin, polystyrene, poly-(4-methylpentene-1), polycarbonate, acrylic resin, an acrylonitrile-butadiene-styrene copolymer, polyester such as polyethylene terephthalate, polyethylene naphthalate, or the like, a butadiene-styrene copolymer, and polyamide (e.g., nylon 6, nylon 6·6, nylon 6·10, or nylon 12). 
         [0071]    The drug holder  14  has a first opening  14   a  formed in one end thereof. The drug container  12  is inserted into the drug holder  14  through the first opening  14   a.    
         [0072]    The drug holder  14  also has ledges  32 ,  34  that project horizontally outwardly from left and right sides of the upper end of the drug holder  14 . The ledges  32 ,  34  have respective holes  32   a ,  34   a  formed vertically therethrough. 
         [0073]    The drug holder  14  houses therein a restraint member  36  for restraining the drug container  12  with respect to the drug holder  14 . The restraint member  36  has a tubular shape, which is open at upper and lower ends thereof. The restraint member  36  has protrusions (not shown) on the outer circumferential surface thereof, which engage in either recesses (not shown) formed in an inner circumferential surface of the drug holder  14 , or holes (not shown) formed in a side wall of the drug holder  14 , for thereby securing the drug container  12  at a predetermined position with respect to the drug holder  14 . 
         [0074]    The restraint member  36  may be made of materials, which are the same as the aforementioned materials of the drug holder  14 . 
         [0075]    The liquid holder  18  is a bottomed tubular component for storing the liquid container  16 . As shown in  FIG. 1 , the liquid holder  18  has a side wall with a height large enough to fully house the liquid container  16  in the liquid holder  18 . 
         [0076]    The liquid holder  18  has a plurality of support guides  19  spaced circumferentially on an inner circumferential surface thereof for supporting the liquid container  16 , and limiting projections  21  on the inner circumferential surface thereof for limiting the depth to which the liquid container  16  can be inserted. 
         [0077]    The liquid holder  18  has a second opening  18   a  formed in an end thereof. The liquid container  16  is inserted into the liquid holder  18  through the second opening  18   a.    
         [0078]    The liquid holder  18  also includes a pair of lock members  38 ,  40  extending downwardly from left and right sides of an outer circumferential surface thereof. The lock members  38 ,  40  include respective arms  38   a ,  40   a , first engaging portions  38   b ,  40   b  disposed on respective distal ends of the arms  38   a ,  40   a , and second engaging portions  38   c ,  40   c  disposed on the arms  38   a ,  40   a  more closely to proximal ends thereof than the first engaging portions  38   b ,  40   b . The arms  38   a ,  40   a  have a plurality of vertically spaced projections  38   d ,  40   d , respectively, on outer side surfaces thereof. 
         [0079]    As shown in  FIG. 1 , the double-ended needle  20  includes a first puncture needle  42  for piercing the first plug  26 , and a second puncture needle  44  for piercing the second plug  30 . The double-ended needle  20  is formed integrally with the connector  22 . 
         [0080]    The connector  22  has a partition  46  extending horizontally, a lower side wall  48  extending downwardly from the partition  46 , and an upper side wall  50  extending upwardly from the partition  46 . The first puncture needle  42  is mounted on the lower surface of the partition  46 , and the second puncture needle  44  is mounted on the upper surface of the partition  46 . The connector  22  may be made of materials, which are the same as the aforementioned materials of the drug holder  14 . 
         [0081]    The lower side wall  48  surrounds the first puncture needle  42 . The lower side wall  48  has a height (vertical dimension) greater than the height of the first puncture needle  42 , so that the distal end (cutting face) of the first puncture needle  42  does not project downwardly from the lower side wall  48 . 
         [0082]    The upper side wall  50  surrounds the second puncture needle  44  and has a shape and size such that the upper side wall  50  can be inserted into the drug container  12 . The upper side wall  50  has a height greater than the height of the second puncture needle  44 , so that the distal end (cutting face) of the second puncture needle  44  does not project upwardly from the upper side wall  50 . The upper side wall  50  has ledges  52 ,  54  projecting horizontally outwardly from left and right sides of an upper end thereof. The ledges  52 ,  54  have respective holes  52   a ,  54   a  formed vertically therethrough. 
         [0083]    The connector  22  can be inserted into the drug holder  14  with the outer circumferential surface of the upper side wall  50  serving as a sliding surface. More specifically, the connector  22  is capable of sliding longitudinally (vertically) along the double-ended needle  20  into fitting engagement with the drug holder  14 . 
         [0084]    The liquid holder  18  can be inserted into the connector  22  such that the outer circumferential surface of the lower end portion thereof serves as a sliding surface. More specifically, the liquid holder  18  can slide longitudinally along the double-ended needle  20  into fitting engagement with the connector  22 . 
         [0085]    According to the first embodiment, the lock members  38 ,  40 , the ledges  32 ,  34 , and the ledges  52 ,  54  jointly make up a lock mechanism  37 . The lock mechanism  37  serves to releasably lock the drug holder  14 , the connector  22 , and the liquid holder  18  inseparably together when the drug holder  14 , the connector  22 , and the liquid holder  18  are fitted together in a relative positional relation, such that the first puncture needle  42  pierces the first plug  26  and the second puncture needle  44  pierces the second plug  30 . 
         [0086]    The lock mechanism  37  can selectively be placed in a first state, as shown in  FIG. 2A , and a second state, as shown in  FIG. 2B . In the first state, the liquid holder  18  engages the connector  22  and the drug holder  14  as a whole. In the second state, the liquid holder  18  engages the connector  22 , but is disengaged from the drug holder  14 . 
         [0087]    Since the ledges  32 ,  34  of the drug holder  14  are identical in constitution, the right ledge  34  will typically be described below. Similarly, since the lock members  38 ,  40  and the ledges  52 ,  54  of the connector  22  are identical in constitution, the right lock member  40  and the right ledge  54  will typically be described below. Since the ledge  34 , the lock member  40 , and the ledge  54  are provided in respective pairs, the first state and the second state can be reliably achieved. 
         [0088]    As shown in  FIGS. 1 ,  2 A and  2 B, the lock member  40  includes a plate-like arm  40   a  projecting from the outer circumferential surface of the side wall of the liquid holder  18 , a first engaging portion  40   b  projecting from one surface  401  of the arm  40   a , and a second engaging portion  40   c  projecting from another surface  402  of the arm  40   a.    
         [0089]    The other surface  402  of the arm  40   a  faces toward the side wall of the liquid holder  18 . The arm  40   a  has one end (an upper end as shown) supported on and fixed to the side wall of the liquid holder  18 . Thus, the arm  40   a  is supported in a cantilevered fashion and can be elastically deformed when the arm  40   a  is pressed at a certain location on a floating portion thereof toward the side wall of the liquid holder  18 . The arm  40   a  is of a crank shape as viewed in side elevation, or more specifically, the arm  40   a  is spaced from the side wall of the liquid holder  18  by a distance that increases stepwise toward the other end thereof (a lower end as shown). 
         [0090]    As shown in  FIGS. 2A and 2B , the first engaging portion  40   b  is constituted as a prong, which projects from the distal end of the arm  40   a . The first engaging portion  40   b  has a slanted surface  403  inclined with respect to the vertical direction, and a horizontal engaging surface  404  opposite to the slanted surface  403 . 
         [0091]    The second engaging portion  40   c  is constituted as a prong, which projects from the arm  40   a  at a position above the first engaging portion  40   b . The second engaging portion  40   c  has a slanted surface  405  inclined with respect to the vertical direction, and a horizontal engaging surface  406  opposite to the slanted surface  405 . 
         [0092]    As shown in  FIG. 2A , the ledge  34  of the drug holder  14  can engage with the first engaging portion  40   b . In an assembled state, the arm  40   a  can be inserted into the hole  34   a  in the ledge  34 . When the liquid holder  18  is connected, i.e., is inserted into, the drug holder  14 , the arm  40   a  is inserted into the hole  34   a  in the ledge  34 . At this time, the slanted surface  403  of the first engaging portion  40   b  of the arm  40   a  presses against and then moves over and beyond the inner circumferential surface of the hole  34   a . When the slanted surface  403  of the first engaging portion  40   b  moves over and beyond the inner circumferential surface of the hole  34   a , the arm  40   a  snaps back under its own resilient force, thereby causing the engaging surface  404  to engage with the lower surface of the ledge  34 , as shown in  FIG. 2A . In this state, the liquid holder  18  and the drug holder  14  engage with each other. In the state shown in  FIG. 2A , a clearance  410  is formed between the other surface  402  of the arm  40   a  and the inner circumferential surface of the hole  34   a  in the ledge  34 . The engaging surface  404  of the first engaging portion  40   b  has a horizontal length slightly smaller than the distance provided by the clearance  410 . 
         [0093]    The arm  40   a  can be elastically deformed from the state shown in  FIG. 2A  by being pressed toward the side wall of the liquid holder  18  over the distance provided by the clearance  410 . When the arm  40   a  is elastically deformed in this manner, the engaging surface  404  of the first engaging portion  40   b  is spaced from the lower surface of the ledge  34  (see  FIG. 2B ). The first engaging portion  40   b  and the ledge  34 , i.e., the liquid holder  18  and the drug holder  14 , do not become disengaged from each other. 
         [0094]    As shown in  FIGS. 2A and 2B , the ledge  54  of the connector  22  engages with the second engaging portion  40   c . In an assembled state, the arm  40   a  can be inserted into the hole  54   a  in the ledge  54 . When the liquid holder  18  is connected, i.e., is inserted into, the drug holder  14 , the arm  40   a  is inserted into the hole  54   a  in the ledge  54 . At this time, the slanted surface  405  of the second engaging portion  40   c  of the arm  40   a  presses against and then moves over and beyond the inner circumferential surface of the hole  54   a . When the slanted surface  405  of the second engaging portion  40   c  moves over and beyond the inner circumferential surface of the hole  54   a , the arm  40   a  snaps back under its own resilient force, thereby causing the engaging surface  406  to engage with the ledge  54 , as shown in  FIG. 2A . In this state, the liquid holder  18  and the connector  22  engage with each other. 
         [0095]    In the state shown in  FIG. 2A , a clearance  412  is formed between the other surface  402  of the arm  40   a  and the inner circumferential surface of the hole  54   a . The engaging surface  406  of the second engaging portion  40   c  has a horizontal length, which is sufficiently smaller than the distance provided by the clearance  412 . Therefore, even in the presence of the clearance  412 , the second engaging portion  40   c  can engage with the ledge  54  sufficiently and reliably. 
         [0096]    Unlike the first engaging portion  40   b , the second engaging portion  40   c  has the engaging surface  406 , which remains in engagement with the ledge  54  even when the arm  40   a  is elastically deformed from the state shown in  FIG. 2A  as a result of being pressed toward the side wall of the liquid holder  18  (regardless of whether the arm  40   a  is pressed or released) (see  FIG. 2B ). 
         [0097]    When the first engaging portions  38   b ,  40   b  of the lock members  38 ,  40  engage with the ledges  32 ,  34 , respectively, of the drug holder  14 , and the second engaging portions  38   c ,  40   c  of the lock members  38 ,  40  engage with the ledges  52 ,  54 , respectively, of the connector  22 , the lock mechanism  37  is placed in the first state, in which the liquid holder  18  engages the connector  22  and the drug holder  14  as a whole. When the arms  38   a ,  40   a  are pressed from the first state, the first engaging portions  38   b ,  40   b  of the lock members  38 ,  40  disengage from the ledges  32 ,  34 , respectively, of the drug holder  14 , while the second engaging portions  38   c ,  40   c  of the lock members  38 ,  40  remain in engagement with the ledges  52 ,  54 , respectively, of the connector  22 . In this condition, the lock mechanism  37  is placed in the second state, in which the liquid holder  18  remains in engagement with the connector  22 , but is disengaged from the drug holder  14 . 
         [0098]    According to a modification of the lock mechanism  37  shown in  FIG. 1 , the drug holder  14  may include lock members similar to the lock members  38 ,  40 , and the liquid holder  18  may include ledges similar to the ledges  32 ,  34  for engaging with the lock members. 
         [0099]      FIG. 3  is an enlarged cross-sectional view, partially omitted from illustration, showing the double-ended needle  20  integral with the connector  22  and nearby parts. As shown in  FIG. 3 , the first puncture needle  42  and the second puncture needle  44  include increased penetration resistance members  64 ,  66 , respectively, disposed at positions closer to proximal end portions thereof (at the partition  46 ) than distal-end tubes  60 ,  62  including cutting faces  56 ,  58 , and having a greater penetration resistance to the first plug  26  and the second plug  30  than the distal-end tubes  60 ,  62 . 
         [0100]    In the first embodiment, according to one configuration, the increased penetration resistance members  64 ,  66  comprise increased diameter members  64 A,  66 A, respectively, having an outside diameter greater than the outside diameter of the distal-end tubes  60 ,  62 . According to another configuration (modification), the increased penetration resistance members  64 ,  66  may have a zigzag shape (sawtooth shape) provided by a vertical array of alternate peaks and valleys on the outer circumferential surfaces of the first puncture needle  42  and the second puncture needle  44 . 
         [0101]    According to the first embodiment, as shown in  FIG. 3 , the first puncture needle  42  and the second puncture needle  44  include an inner tube  68  of metal, which has a relatively small diameter (thin diameter), including the distal-end tubes  60 ,  62  and outer tubes  70 ,  72 , which have a large diameter, and which surround the inner tube  68  so as to provide the increased penetration resistance members  64 ,  66 . The distal ends of the inner tube  68 , which project from the distal ends of the outer tubes  70 ,  72 , serve as the distal-end tubes  60 ,  62 . 
         [0102]    The inner tube  68  may be made of stainless steel, an aluminum alloy, a copper-based alloy, or the like. 
         [0103]    According to the first embodiment, the inner tube  68  comprises a single member shared by the first puncture needle  42  and the second puncture needle  44 . However, the inner tube  68  may comprise separate members, each of which is associated respectively with the first puncture needle  42  and the second puncture needle  44 . 
         [0104]    The outer tubes  70 ,  72  may be made of materials, which are the same as the aforementioned materials of the drug container  12 . 
         [0105]    The outer tubes  70 ,  72  and the partition  46  may be formed integrally, or alternatively, may be separate members, which are secured together by adhesive bonding, welding, or the like. 
         [0106]    According to the first embodiment, as shown in  FIG. 3 , the cutting face  56  of the first puncture needle  42  and the cutting face  58  of the second puncture needle  44  are inclined substantially at the same angle in one direction with respect to the axial direction (vertical direction in  FIG. 3 ) of the double-ended needle  20 . According to a modification of the first embodiment, however, the cutting face  56  of the first puncture needle  42  and the cutting face  58  of the second puncture needle  44  may be inclined in opposite directions with respect to the axial direction. 
         [0107]      FIG. 4  is an enlarged cross-sectional view, partially omitted from illustration, illustrative of dimensions of a distal end portion of the double-ended needle  20  of the mixing instrument  10 . Since the first puncture needle  42  and the second puncture needle  44  basically have the same constitution, the dimensions of the distal end portion of the first puncture needle  42  of the double-ended needle  20  will typically be described below. 
         [0108]    As shown in  FIG. 4 , the outside diameter of the inner tube  68  (distal-end tube  60 ) is represented by P, the outside diameter of the outer tube  70  (increased diameter member  64 A) is represented by Q, the distance in the axial direction from the distal end face of the outer tube  70  to the proximal end of the opening of the inner tube  68  is represented by L 1 , the distance in the axial direction from the distal end face of the outer tube  70  to the distal end of the opening of the inner tube  68  is represented by L 2 , and the angle formed between the axial direction of the inner tube  68  and the cutting face  56  is represented by θ. 
         [0109]    P may be set to a value in a range from 1.20 mm to 1.30 mm (preferably 1.25 mm), for example. Q may be set to a value in a range from 2.25 mm to 2.35 mm (preferably 2.3 mm), for example. L 1  may be set to a value in a range from 0.7 mm to 0.9 mm (preferably 0.8 mm), for example. L 2  may be set to a value in a range from 1.5 mm to 1.7 mm (preferably 1.6 mm), for example. θ may be set to a value in a range from 55° to 60° (preferably 57°). The difference Q−P is preferably in a range from 0.95 to 1.15 mm. 
         [0110]    In the illustrated mixing instrument  10 , P is set to 1.25, Q is set to 2.3 mm, L 1  is set to 0.8 mm, L 1  is set to 1.6 mm, and θ is set to 57°. The thickness of the plug  26  is set to 3 mm. 
         [0111]    The mixing instrument  10  according to the first embodiment is basically constituted as described above. Operations and advantages of the mixing instrument  10  will be described below. 
         [0112]    As shown in  FIG. 1 , the drug container  12  is stored in the drug holder  14  and is secured to the drug holder  14  by the restraint member  36 . The liquid container  16  is mounted in the liquid holder  18  and is held by the liquid holder  18 . 
         [0113]    Then, the connector  22 , with the double-ended needle  20  installed therein, is inserted into the drug holder  14 , such that the first puncture needle  42  is oriented toward the drug container  12 . The liquid holder  18 , with the liquid container  16  mounted therein, is inserted into the connector  22 , such that the second plug  30  is oriented toward the second puncture needle  44 . 
         [0114]    During the insertion process, as shown in  FIGS. 5 and 6 , the distal-end tubes  60 ,  62  (the portions of the inner tube  68  that project from the outer tubes  70 ,  72 ) of the first puncture needle  42  and the second puncture needle  44  pierce (are inserted into) the first plug  26  and the second plug  30 . Also, distal ends of the outer tubes  70 ,  72 , which provide the increased diameter members  64 A,  66 A that function as the increased penetration resistance members  64 ,  66 , abut against the first plug  26  and the second plug  30 , respectively, thereby temporarily preventing the distance that the first puncture needle  42  penetrates into the first plug  26  from increasing, and also temporarily preventing the distance that the second puncture needle  44  penetrates into the second plug  30  from increasing. 
         [0115]    Such a state occurs because the increased diameter members  64 A,  66 A are larger in diameter than the distal-end tubes  60 ,  62 , and hence the increased diameter members  64 A,  66 A exert an increased penetration resistance, such that the increased diameter members  64 A,  66 A cannot be inserted into the first plug  26  and the second plug  30  until after the distal-end tubes  60 ,  62  on the opposite ends have been inserted fully into the first plug  26  and the second plug  30 . 
         [0116]    As shown in  FIG. 6 , since the height h in the axial direction of the cutting face  56  ( 58 ) of the distal-end tube  60  ( 62 ) is smaller than the thickness t of the portion of the first plug  26  (the second plug  30 ), which is pierced by the first puncture needle  42  (the second puncture needle  44 ), when the distal end of the first puncture needle  42  is pushed into the first plug  26 , the opening at the distal end of the first puncture needle  42  is closed by the first plug  26 , and when the distal end of the second puncture needle  44  is pushed into the second plug  30 , the opening at the distal end of the second puncture needle  44  is closed by the second plug  30 . In other words, both the opening of the first puncture needle  42  and the opening of the second puncture needle  44  become closed. As shown in  FIG. 6 , the reverse side of the portion of the first plug  26 , which is pierced by the first puncture needle  42 , has a recess  26   a  formed therein, thereby allowing that portion of the first plug  26  to be pierced easily. The reverse side of the portion of the second plug  30 , which is pierced by the second puncture needle  44 , has a similar recess formed therein. 
         [0117]    When the liquid holder  18  is pushed further toward the drug holder  14  from the state shown in  FIG. 5 , the mixing instrument  10  is assembled as shown in  FIG. 7 . The lock mechanism  37  is easily brought into the first state, as described above. More specifically, the first engaging portions  38   b ,  40   b  of the arms  38   a ,  40   a  engage with the ledges  32 ,  34 , respectively, of the drug holder  14 , whereas the second engaging portions  38   c ,  40   c  of the arms  38   a ,  40   a  engage with the ledges  52 ,  54 , respectively, of the connector  22 . In this manner, the lock mechanism  37  operates to limit the mutual positional relation between the drug container  12  and the liquid container  16 , i.e., to prevent the containers  12 ,  16  from unduly moving, thereby reliably keeping the drug container  12  and the liquid container  16  in fluid communication with each other. 
         [0118]    At this time, as shown in  FIG. 7 , the increased diameter members  64 A,  66 A of the first puncture needle  42  and the second puncture needle  44  pierce and penetrate the first plug  26  and the second plug  30 . Therefore, the needle points (i.e., the cutting faces) of the first puncture needle  42  and the second puncture needle  44  move respectively into the drug container  12  and the liquid container  16 . Thus, the drug container  12  and the liquid container  16  are brought into fluid communication with each other through the double-ended needle  20 . 
         [0119]    Inasmuch as a negative pressure is developed in the drug container  12 , the liquid in the liquid container  16  is attracted to and flows into the drug container  12  through the double-ended needle  20 . Thereafter, in order to mix the drug and the liquid in the drug container  12 , the mixing instrument  10  is shaken several times. At this time, the drug in the drug container  12  becomes diluted and dissolved by the liquid, which has flowed into the drug container  12 . 
         [0120]    After mixing of the first component and the second component is completed, the arms  38   a ,  40   a  of the lock members  38 ,  40  on the liquid holder  18  are pressed inwardly toward the liquid holder  18 . The first engaging portions  38   b ,  40   b  of the arms  38   a ,  40   a  disengage from the ledges  32 ,  34  of the drug holder  14 , whereas the second engaging portions  38   c ,  40   c  of the arms  38   a ,  40   a  remain in engagement with the ledges  52 ,  54  of the connector  22 . In other words, the lock mechanism  37  is brought into the second state. 
         [0121]    Then, the liquid holder  18  is pulled upwardly. The liquid holder  18 , in which the liquid container  16  is held, can now be released (removed) from the drug holder  14  together with the connector  22 . Since the projections  38   d ,  40   d  are disposed on the outer circumferential surfaces of the arms  38   a ,  40   a , the user finds it easy to pull the liquid holder  18 , because the projections  38   d ,  40   d  function as a slip stop when the user presses the arms  38   a ,  40   a  laterally inward. 
         [0122]    Then, the drug holder  14 , from which the connector  22  has been removed, is vertically inverted. Then, the left and right side walls of the drug holder  14  are pressed inwardly to release the restraint member  36  out of engagement with the drug holder  14 . The drug container  12  is released (drops) from the drug holder  14  together with the restraint member  36 . 
         [0123]    According to the first embodiment, as described above, the cutting face  56  of the first puncture needle  42  and the cutting face  58  of the second puncture needle  44  are inclined in one direction with respect to the axial direction. With this arrangement, when the first puncture needle  42  and the second puncture needle  44  pierce the first plug  26  and the second plug  30 , respectively, forces acting horizontally on the first puncture needle  42  and the second puncture needle  44  cancel each other out. Therefore, the connector  22  is prevented from being pressed against the inner circumferential surface of the drug holder  14 , with the result that sliding resistance between the connector  22  and the drug holder  14  is prevented from increasing when the connector  22  is inserted into the drug holder  14 . 
         [0124]    According to the first embodiment, as described above, the first puncture needle  42  and the second puncture needle  44  have respective distal-end tubes  60 ,  62  with openings formed in the cutting faces on the distal ends thereof. The increased penetration resistance members  64 ,  66  (the increased diameter members  64 A,  66 A) are disposed at positions closer to the proximal end portions than the distal-end tubes  60 ,  62 , and have a greater penetration resistance to the first plug  26  and the second plug  30  than the distal-end tubes  60 ,  62 . Therefore, when the double-ended needle  20  is connected to the drug container  12  and the liquid container  16 , the distal-end tubes  60 ,  62 , including the needle points with relatively small penetration resistance, initially are inserted into the first plug  26  and the second plug  30 . Thereafter, the increased penetration resistance members  64 ,  66 , with relatively large penetration resistance, are inserted into the first plug  26  and the second plug  30 . 
         [0125]    After the openings in the needle points of the first puncture needle  42  and the second puncture needle  44  have been closed respectively by the first plug  26  and the second plug  30 , the first puncture needle  42  and the second puncture needle  44  penetrate the first plug  26  and the second plug  30 , respectively. Consequently, negative pressure in the drug container  12  is maintained, and liquid is prevented from leaking out, even if the timing at which the first puncture needle  42  penetrates the first plug  26  differs from the timing at which the second puncture needle  44  penetrates the second plug  30 . 
         [0126]    More specifically, even if the first puncture needle  42  penetrates the first plug  26  before the second puncture needle  44  has penetrated the second plug  30 , since the opening in the distal end of the second puncture needle  44  is closed by the second plug  30 , negative pressure in the drug container  12  is maintained. Even if the second puncture needle  44  penetrates the second plug  30  before the first puncture needle  42  has penetrated the first plug  26 , since the opening in the distal end of the first puncture needle  42  is closed by the first plug  26 , liquid is prevented from leaking out. Accordingly, a mixing instrument  10  is provided, which can be handled easily without causing handling errors, and a piercing method is provided, which allows a double-ended needle  20  to pierce plugs simply without handling errors. 
         [0127]    According to the first embodiment, since the increased penetration resistance members  64 ,  66  comprise the increased diameter members  64 A,  66 A, respectively, each having an outside diameter greater than the outside diameter of the distal-end tubes  60 ,  62 , penetration resistance is increased with a simple arrangement, i.e., by a step, which is provided by the different outside diameters of the distal-end tubes  60 ,  62  and the increased diameter members  64 A,  66 A. 
         [0128]    According to the first embodiment, since the distal-end tubes  60 ,  62  including the cutting edges are made of metal, the cutting edges can easily be formed as sharp edges. The cutting edges, which are formed as sharp edges, reduce the penetration resistance of the distal-end tubes  60 ,  62  with respect to the first plug  26  and the second plug  30 , thereby reducing forces required to cause the distal-end tubes  60 ,  62  to pierce the first plug  26  and the second plug  30 . The mixing instrument  10  can thus be handled more easily. 
         [0129]    According to the first embodiment, when the drug holder  14 , the connector  22 , and the liquid holder  18  are fitted together, the components slide against each other and are guided for relative axial movement. Therefore, the first puncture needle  42  and the second puncture needle  44  can pierce the first plug  26  and the second plug  30 , respectively, accurately and simply in the axial direction. Therefore, the mixing instrument  10  can be handled more easily. 
         [0130]    According to the first embodiment, when the drug holder  14 , the connector  22 , and the liquid holder  18  are coupled together, the components are locked by the lock mechanism  37 , so that the drug holder  14 , the connector  22 , and the liquid holder  18  can be handled in their entirety as an integrated mixing instrument  10 . Consequently, it is easy to perform the process of shaking the mixing instrument  10  in order to accelerate mixing of the first component and the second component. 
         [0131]      FIG. 8A  is an enlarged cross-sectional view, partially omitted from illustration, showing a first modification of the double-ended needle  20 , which is of the basic form according to the first embodiment of the present invention. With the basic form according to the first embodiment, the inner tube  68  provides the small-diameter distal-end tubes  60 ,  62 , and the outer tubes  70 ,  72  provide the large-diameter increased diameter members  64 A,  66 A. According to the first modification shown in  FIG. 8A , a double-ended needle  71  may comprise a first puncture needle  73  and a second puncture needle  74 , including distal-end tubes  76 ,  78  and increased diameter members  80 ,  82 , which are integral with each other. The first puncture needle  73  and the second puncture needle  74  may be made of materials, which are the same as the aforementioned materials of the drug holder  14 . 
         [0132]      FIG. 8B  is an enlarged cross-sectional view, partially omitted from illustration, showing a second modification of the double-ended needle  20 , which is of the basic form according to the first embodiment of the present invention. According to the second modification shown in  FIG. 8B , a double-ended needle  90  may include increased penetration resistance members  96 ,  98  in the form of projections  64 B,  66 B, which are integral therewith, near distal end portions of a first puncture needle  92  and a second puncture needle  94 , respectively. The projections  64 B,  66 B may be annular protrusions that extend fully around the outer circumferential surfaces of the first puncture needle  92  and the second puncture needle  94 , or protrusions that extend less than fully around the outer circumferential surfaces of the first puncture needle  92  and the second puncture needle  94 . The projections  64 B,  66 B may be a plurality of protrusions, which are spaced longitudinally (axially) along the first puncture needle  92  and the second puncture needle  94 . 
       Second Embodiment 
       [0133]      FIG. 9  is an exploded perspective view of a mixing instrument  100  according to a second embodiment of the present invention.  FIG. 10  is a cross-sectional view of the mixing instrument  100  according to the second embodiment of the present invention. 
         [0134]    As shown in  FIGS. 9 and 10 , the mixing instrument  10  includes two drug containers (first containers)  112 A,  112 B for storing a first component therein in a solid phase or a liquid phase, a drug holder (first holder)  114  in which the two drug containers  112 A,  112 B are mounted, two liquid containers (second containers)  116 A,  116 B for storing a second component in a liquid phase, a liquid holder (second holder)  118  in which two liquid containers  116 A,  116 B are mounted, two double-ended needles  120 A,  120 B, which are capable of bringing the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B into fluid communication with each other, and a connector  122  to which the double-ended needles  120 A,  120 B are fixed. According to the first embodiment, the drug container  12 , the liquid container  16 , and the double-ended needle  20  each are provided as a single part. However, according to the second embodiment, such components are provided as two parts each. 
         [0135]    The drug containers  112 A,  112 B are basically of the same constitution as the drug container  12 . The two drug containers  112 A,  112 B have substantially the same constitution, except that the drug containers  112 A,  112 B differ in size and shape from each other. A negative pressure is developed in each of the drug containers  112 A,  112 B. 
         [0136]    The liquid containers  116 A,  116 B are basically of the same constitution as the liquid container  16 . The two liquid containers  116 A,  116 B are substantially of the same constitution, except that they differ in size and shape from each other. 
         [0137]    The first component stored in the drug containers  112 A,  112 B may be the same drug as the first component stored in the above-described drug container  12 . 
         [0138]    The second component stored in the liquid containers  116 A,  116 B may be the same liquid as the second component stored in the above-described liquid container  16 . 
         [0139]    The drug holder  114  is a bottomed tubular component, which stores the two drug containers  112 A,  112 B therein. The drug holder  114  is made of materials, which are the same as the aforementioned materials of the drug holder  14 . 
         [0140]    The drug holder  114  has a first opening  114   a  formed in one end thereof. The drug containers  112 A,  112 B are inserted into the drug holder  114  through the first opening  114   a.    
         [0141]    The drug holder  114  also has ledges  132 ,  134 , which project horizontally outwardly from left and right sides of the upper end thereof. The ledges  132 ,  134  have respective holes  132   a ,  134   a  formed vertically therethrough. 
         [0142]    The drug holder  114  houses therein a restraint member  136  for restraining the two drug containers  112 A,  112 B with respect to the drug holder  114 . The restraint member  136  includes a pair of tubular members  137 A,  137 B, which are open at upper and lower ends thereof, and a joint  139  that interconnects the tubular members  137 A,  137 B. 
         [0143]    The restraint member  136  also has an engaging protrusion  141  disposed between the tubular members  137 A,  137 B. When the engaging protrusion  141  engages in an engaging recess  143 , which is formed in an inner surface of the drug holder  114 , the drug containers  112 A,  112 B become fixed in position with respect to the drug holder  114 . Instead of the engaging recess  143 , the drug holder  114  may have a hole formed in a side wall thereof, and the engaging protrusion  141  may engage in the hole. 
         [0144]    The restraint member  136  may be made of materials, which are the same as the aforementioned materials of the drug holder  14 . 
         [0145]    The liquid holder  118  is a bottomed tubular component for storing the two liquid containers  116 A,  116 B. As shown in  FIG. 10 , the liquid holder  118  has a plurality of support guides  119 A,  119 B provided on the inner circumferential surface thereof for supporting the two liquid containers  116 A,  116 B, and a plurality of limiting projections  121 A,  121 B provided on the inner circumferential surface thereof for limiting the depth at which the liquid containers  116 A,  116 B can be inserted. 
         [0146]    The liquid holder  118  includes a second opening  118   a  formed in one end thereof. The liquid containers  116 A,  116 B are inserted into the liquid holder  118  through the second opening  118   a.    
         [0147]    The liquid holder  118  also includes a pair of lock members  138 ,  140  extending downwardly from left and right sides of the outer circumferential surface thereof. The lock members  38 ,  40  include respective arms  138   a ,  140   a , first engaging portions  138   b ,  140   b , which are disposed on respective distal ends of the arms  138   a ,  140   a , and second engaging portions  138   c ,  140   c , which are disposed on the arms  138   a ,  140   a  more closely to the proximal ends (i.e., the upper ends thereof, as illustrated) than the first engaging portions  138   b ,  140   b . The arms  138   a ,  140   a  have a plurality of vertically spaced projections  138   d ,  140   d  provided respectively on outer side surfaces thereof. 
         [0148]    According to the second embodiment, the lock members  138 ,  140 , the ledges  132 ,  134 , and the ledges  152 ,  154  jointly make up a lock mechanism  137 . The lock mechanism  137  serves to releasably lock the drug holder  114 , the connector  122 , and the liquid holder  118  inseparably when the drug holder  114 , the connector  122 , and the liquid holder  118  are fitted together in a relative positional relation, such that the first puncture needles  142 A,  142 B pierce the first plugs  126 A,  126 B and the second puncture needles  144 A,  144 B pierce the second plugs  130 A,  130 B. 
         [0149]    The lock mechanism  137  can selectively be placed in a first state, in which the liquid holder  118  engages the connector  122  and the drug holder  114  as a whole, and a second state, in which the liquid holder  118  engages the connector  122  but is disengaged from the drug holder  114 . The constitution and functions of the lock mechanism  137  are the same as those of the lock mechanism  37  according to the first embodiment, and such features will not be described in detail below. 
         [0150]    According to a modification of the lock mechanism  137 , lock members, which are similar to the lock members  138 ,  140 , may be provided on the drug holder  114 , and ledges, which are similar to the ledges  132 ,  134 , may be provided on the liquid holder  118  for engaging with the lock members. 
         [0151]    As shown in  FIGS. 9 and 10 , the two double-ended needles  120 A,  120 B have respective first puncture needles  142 A,  142 B that pierce the first plugs  126 A,  126 B, respectively, and respective second puncture needles  144 A,  144 B that pierce the second plugs  130 A,  130 B, respectively. The two double-ended needles  120 A,  120 B are joined to each other integrally by the connector  122 . 
         [0152]    The two first puncture needles  142 A,  142 B and the two second puncture needles  144 A,  144 B have increased penetration resistance members  164 ,  165 ,  166 ,  167 , respectively, disposed at positions closer to proximal end portions thereof (i.e., on the partition  146 ) than the distal-end tubes  160 A,  160 B,  162 A,  162 B including cutting faces, and having a greater penetration resistance with respect to the first plugs  126 A,  126 B and the second plugs  130 A,  130 B than the distal-end tubes  160 A,  160 B,  162 A,  162 B. 
         [0153]    In the second embodiment, according to one configuration, the increased penetration resistance members  164 ,  165 ,  166 ,  167  comprise increased diameter members  164 A,  165 A,  166 A,  167 B, respectively, having an outside diameter greater than the outside diameter of the distal-end tubes  160 A,  160 B,  162 A,  162 B. According to another configuration (modification), the increased penetration resistance members  164 ,  165 ,  166 ,  167  may have a zigzag shape (sawtooth shape) provided by a vertical array of alternate peaks and valleys on outer circumferential surfaces of the first puncture needles  142 A,  142 B and the second puncture needles  144 A,  144 B. 
         [0154]    According to the second embodiment, the two first puncture needles  142 A,  142 B and the two second puncture needles  144 A,  144 B include inner tubes  168 A,  168 B made of metal, which are relatively small (thin) in diameter, including the distal-end tubes  160 A,  160 B,  162 A,  162 B, together with outer tubes  170 A,  170 B,  172 A,  172 B, which are relatively large in diameter, and which surround the inner tubes  168 A,  168 B and serve to provide the increased penetration resistance members  164 ,  165 ,  166 ,  167 . The distal ends of the inner tubes  168 A,  168 B, which project from the distal ends of the outer tubes  170 A,  170 B,  172 A,  172 B, serve as the distal-end tubes  160 A,  160 B,  162 A,  162 B. 
         [0155]    The inner tubes  168 A,  168 B may be made of materials, which are the same as the aforementioned materials of the inner tube  68  according to the first embodiment. The outer tubes  170 A,  170 B,  172 A,  172 B may be made of materials, which are the same as the aforementioned materials of the outer tubes  70 ,  72  according to the first embodiment. 
         [0156]    According to the second embodiment, one of the inner tubes  168 A comprises a single member, which is shared by the first puncture needle  142 A and the second puncture needle  144 A. However, the inner tube  168 A may comprise separate members associated respectively with the first puncture needle  142 A and the second puncture needle  144 A. The same holds true for the other inner tube  168 B. 
         [0157]    The outer tubes  170 A,  170 B,  172 A,  172 B may be made of materials, which are the same as the aforementioned materials of the drug containers  112 A,  112 B. 
         [0158]    The outer tubes  170 A,  170 B,  172 A,  172 B and the partition  146  may be formed integrally with each other, or alternatively, the outer tubes  170 A,  170 B,  172 A,  172 B may be separate members secured together by adhesive bonding, welding, or the like. 
         [0159]    According to the second embodiment, the cutting faces of the first puncture needles  142 A,  142 B and the cutting faces of the second puncture needles  144 A,  144 B are inclined in opposite directions with respect to the axial direction of the double-ended needles  120 A,  120 B, at substantially the same absolute angle. The angle is set such that the gradients of one of the first puncture needles  142 A and the other first puncture needle  142 B are mirror images of each other (in point symmetry) with respect to a vertical line that extends between the double-ended needles  120 A,  120 B. Similarly, the angle is set such that the gradients of one of the second puncture needles  144 A and the other second puncture needle  144 B are mirror images of each other (in point symmetry) with respect to a vertical line that extends between the double-ended needles  120 A,  120 B. 
         [0160]    According to a modification of the second embodiment, however, the cutting faces of the first puncture needles  142 A,  142 B and the cutting faces of the second puncture needles  144 A,  144 B may be inclined in one direction with respect to the axial direction, as is the case with the double-ended needle  20  according to the first embodiment shown in  FIG. 2 . 
         [0161]    The connector  122  has a partition  146  extending horizontally, a lower side wall  148  extending downwardly from the partition  146 , and an upper side wall  150  extending upwardly from the partition  146 . The two first puncture needles  142 A,  142 B are mounted on the lower surface of the partition  146 , whereas the two second puncture needles  144 A,  144 B are mounted on the upper surface of the partition  146 . The connector  122  may be made of materials, which are the same as the aforementioned materials of the drug holder  14 . 
         [0162]    The lower side wall  148  surrounds the two first puncture needles  142 A,  142 B as a whole. The lower side wall  148  has a height (vertical dimension), which is greater than the height of the two first puncture needles  142 A,  142 B, so that the distal ends (cutting faces) of the two first puncture needles  142 A,  142 B do not project downwardly from the lower end of the lower side wall  148 . 
         [0163]    The upper side wall  150  surrounds the two second puncture needles  144 A,  144 B in their entirety. The upper side wall  150  has a height greater than the height of the two second puncture needles  144 A,  144 B, so that the distal ends (cutting faces) of the two second puncture needles  144 A,  144 B do not project upwardly from the upper side wall  150 . The upper side wall  150  has ledges  152 ,  154  projecting horizontally outwardly from the left and right sides of the upper end thereof. The ledges  152 ,  154  have respective holes  152   a ,  154   a  formed vertically therethrough. 
         [0164]    The connector  122  can be inserted into the drug holder  114 , with the outer circumferential surface of the upper side wall  150  thereof serving as a sliding surface. More specifically, the connector  122  can move longitudinally (vertically) along the double-ended needles  120 A,  120 B with respect to the drug holder  114 . 
         [0165]    The liquid holder  118  can be inserted into the connector  122  with the outer circumferential surface of the lower end portion thereof serving as a sliding surface. More specifically, the liquid holder  118  is capable of moving longitudinally along the double-ended needles  120 A,  120 B with respect to the connector  122 . 
         [0166]    The dimensions and angles of the distal end portions of the two double-ended needles  120 A,  120 B may be set in the same manner as the dimensions P, Q, L 1 , L 2  and the angle θ (see  FIG. 4 ) of the aforementioned corresponding portions according to the first embodiment. 
         [0167]    The mixing instrument  100  according to the second embodiment is basically constituted as described above. Operations and advantages of the mixing instrument  100  will be described below. 
         [0168]    As shown in  FIG. 10 , the drug containers  112 A,  112 B are stored in the drug holder  114 , and are secured to the drug holder  114  by the restraint member  136 . The liquid containers  116 A,  116 B are mounted in the liquid holder  118  and are held by the liquid holder  118 . 
         [0169]    Then, the connector  122 , with the two double-ended needles  120 A,  120 B installed therein, is inserted into the drug holder  114  such that the two first puncture needles  142 A,  142 B are oriented toward the drug containers  112 A,  112 B. Further, the liquid holder  118 , with the two liquid containers  116 A,  116 B mounted therein, is inserted into the connector  122  such that the second plugs  130 A,  130 B are oriented toward the second puncture needles  144 A,  144 B. 
         [0170]    During the insertion process, as shown in  FIG. 11 , the distal-end tubes  160 A,  160 B,  162 A,  162 B (i.e., the portions of the inner tubes  168 A,  168 B that project from the outer tubes  170 A,  170 B,  172 A,  172 B) of the first puncture needles  142 A,  142 B and the second puncture needles  144 A,  144 B pierce (are inserted into) the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, and the distal ends of the outer tubes  170 A,  170 B,  172 A,  172 B, which provide the increased diameter members  164 A,  165 A,  166 A,  167 A that function as the increased penetration resistance members  164 ,  165 ,  166 ,  167 , abut against the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively, thereby temporarily preventing the distance by which the first puncture needles  142 A,  142 B are inserted into the first plugs  126 A,  126 B from increasing, as well as temporarily preventing the distance by which the second puncture needles  144 A,  144 B are inserted into the second plugs  130 A,  130 B from increasing. 
         [0171]    Such a condition occurs because the increased diameter members  164 A,  165 A,  166 A,  167 A are larger in diameter than the distal-end tubes  160 A,  160 B,  162 A,  162 B, and hence the increased diameter members  164 A,  165 A,  166 A,  167 A exert an increased penetration resistance, such that the increased diameter members  164 A,  165 A,  166 A,  167 A cannot be inserted into the first plugs  126 A,  126 B and the second plugs  130 A,  130 B until after the distal-end tubes  160 A,  160 B,  162 A,  162 B on the opposite ends thereof have been inserted fully into the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. 
         [0172]    Since the height in the axial direction of the cutting faces of the distal-end tubes  160 A,  160 B,  162 A,  162 B is smaller than the thickness of the portions of the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, which are pierced by the first puncture needles  142 A,  142 B and the second puncture needles  144 A,  144 B, the openings at the distal ends of the first puncture needles  142 A,  142 B are closed by the first plugs  126 A,  126 B, and the openings at the distal ends of the second puncture needles  144 A,  144 B are closed by the second plugs  130 A,  130 B. In other words, both openings of the first puncture needles  142 A,  142 B and both openings of the second puncture needles  144 A,  144 B are closed. 
         [0173]    When the liquid holder  118  is further pushed toward the drug holders  114  from the state shown in  FIG. 11 , the mixing instrument  100  is assembled together, as shown in  FIG. 12 . The lock mechanism  137  is easily brought into the first state, as described above. More specifically, the first engaging portions  138   b ,  140   b  of the arms  138   a ,  140   a  engage with the respective ledges  132 ,  134  of the drug holder  114 , and the second engaging portions  138   c ,  140   c  of the arms  138   a ,  140   a  engage the respective ledges  152 ,  154  of the connector  122 . The lock mechanism  137  thus operates to limit the mutual positional relation between the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B, i.e., to prevent the containers  112 A,  112 B,  116 A,  116 B from unduly moving, thereby reliably maintaining the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B in fluid communication with each other. 
         [0174]    At this time, as shown in  FIG. 12 , the increased diameter members  164 A,  165 A,  166 A,  167 A of the first puncture needles  142 A,  142 B and the second puncture needles  144 A,  144 B pierce the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively, and the needle points (the cutting faces) of the first puncture needles  142 A,  142 B and the second puncture needles  144 A,  144 B move respectively into the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B. At this time, the two drug containers  112 A,  112 B and the two liquid containers  116 A,  116 B are brought into fluid communication with each other by the corresponding double-ended needles  120 A,  120 B. 
         [0175]    Inasmuch as a negative pressure is developed in the two drug containers  112 A,  112 B, liquid in the liquid containers  116 A,  116 B is attracted to and flows into the drug containers  112 A,  112 B through the two double-ended needles  120 A,  120 B. Thereafter, the mixing instrument  100  is shaken several times. At this time, the drugs in the drug containers  112 A,  112 B become diluted and are dissolved by the liquids that flow into the drug containers  112 A,  112 B. 
         [0176]    After mixing of the drug and the liquid is completed, the arms  138   a ,  140   a  of the lock members  138 ,  140  on the liquid holder  118  are pressed inwardly toward the liquid holder  118 . The first engaging portions  138   b ,  140   b  of the arms  138   a ,  140   a  disengage from the ledges  132 ,  134  of the drug holder  114 , whereas the second engaging portions  138   e ,  140   e  of the arms  138   a ,  140   a  remain in engagement with the ledges  152 ,  154  of the connector  122 . In other words, the lock mechanism  137  is brought into the second state. 
         [0177]    Then, the liquid holder  118  is pulled upwardly. The liquid holder  118 , which holds the liquid containers  116 A,  116 B therein, can now be released (removed) from the drug holder  114  together with the connector  122 . Since the projections  138   d ,  140   d  are disposed on the arms  138   a ,  140   a , the user finds it easy to pull the liquid holder  118 , because the projections  138   d ,  140   d  function as a slip stop. 
         [0178]    Then, the drug holder  114 , from which the connector  122  has been removed, is vertically inverted. Then, the left and right side walls of the drug holder  114  are pressed inwardly to cause the engaging protrusion  141  of the restraint member  136  to disengage from the engaging recess  143  of the drug holder  114 . The drug containers  112 A,  112 B are released (drop) from the drug holder  114  together with the restraint member  136 . 
         [0179]    According to the second embodiment, as described above, the cutting faces of the first puncture needles  142 A,  142 B and the cutting faces of the second puncture needles  144 A,  144 B are inclined in opposite directions with respect to the axial direction, and one of the double-ended needles  120 A and the other double-ended needle  120 B are mirror images of each other. With this arrangement, when the two double-ended needles  120 A,  120 B pierce into the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively, forces acting horizontally on the two double-ended needles  120 A,  120 B cancel each other out. Therefore, sliding resistance between the connector  122  and the drug holder  114  is prevented from increasing when the connector  122  is inserted into the drug holder  114 . 
         [0180]    According to the second embodiment, as described above, the first puncture needles  142 A,  142 B and the second puncture needles  144 A,  144 B have respective distal-end tubes  160 A,  160 B,  162 A,  162 B with openings formed in the cutting faces on distal ends thereof, and the increased penetration resistance members  164 ,  165 ,  166 ,  167  (increased diameter members  164 A,  165 A,  166 A,  167 A), which are disposed at positions closer to proximal end portions thereof than the distal-end tubes  160 A,  160 B,  162 A,  162 B, and having a greater penetration resistance to the first plugs  126 A,  126 B and the second plugs  130 A,  130 B than the distal-end tubes  160 A,  160 B,  162 A,  162 B. Therefore, when the double-ended needles  120 A,  120 B are connected to the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B, the distal-end tubes  160 A,  160 B,  162 A,  162 B, which include the needle points with a relatively small penetration resistance, are inserted initially into the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, and then the increased penetration resistance members  164 ,  165 ,  166 ,  167 , which have a relatively large penetration resistance, are inserted into the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. 
         [0181]    After the openings in the needle points of the first puncture needles  142 A,  142 B and the second puncture needles  144 A,  144 B have been closed respectively by the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, the first puncture needles  142 A,  142 B and the second puncture needles  144 A,  144 B penetrate the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively. Consequently, negative pressure in the drug containers  112 A,  112 B is maintained and liquids are prevented from leaking out, even if the timing at which the first puncture needles  142 A,  142 B penetrate the first plugs  126 A,  126 B differs from the timing at which the second puncture needles  144 A,  144 B penetrate the second plugs  130 A,  130 B. 
         [0182]    More specifically, even if the first puncture needles  142 A,  142 B penetrate the first plugs  126 A,  126 B before the second puncture needles  144 A,  144 B penetrate the second plugs  130 A,  130 B, since the openings in the distal ends of the second puncture needles  144 A,  144 B are closed by the second plugs  130 A,  130 B, negative pressure in the drug containers  112 A,  112 B is maintained. Further, even if the second puncture needles  144 A,  144 B penetrate the second plugs  130 A,  130 B before the first puncture needles  142 A,  142 B penetrate the first plugs  126 A,  126 B, since the openings in the distal ends of the first puncture needles  142 A,  142 B are closed by the first plugs  126 A,  126 B, liquids are prevented from leaking out. Accordingly, a mixing instrument  100  is provided, which can be handled easily without causing handling errors, while in addition, a piercing method is provided for allowing double-ended needles  120 A,  120 B to pierce plugs simply without handling errors, by maintaining negative pressure in the drug containers  112 A,  112 B and preventing liquids from leaking out, even if the timing at which the first puncture needles  142 A,  142 B penetrate the first plugs  126 A,  126 B differs from the timing at which the second puncture needles  144 A,  144 B penetrate the second plugs  130 A,  130 B. 
         [0183]    According to the second embodiment, since the increased penetration resistance members  164 ,  165 ,  166 ,  167  comprise the increased diameter members  164 A,  165 A,  166 A,  167 A, respectively, which have an outside diameter greater than the outside diameter of the distal-end tubes  160 A,  160 B,  162 A,  162 B, penetration resistance is increased with a simple arrangement, due to the step, which is formed by the different outside diameters of the distal-end tubes  160 A,  160 B,  162 A,  162 B and the increased diameter members  164 A,  165 A,  166 A,  167 A. 
         [0184]    According to the second embodiment, since the distal-end tubes  160 A,  160 B,  162 A,  162 B including the cutting edges are made of metal, the cutting edges can easily be formed as sharp edges. The cutting edges, which are formed as sharp edges, reduce the penetration resistance of the distal-end tubes  160 A,  160 B,  162 A,  162 B with respect to the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, thereby reducing the forces required to cause the distal-end tubes  160 A,  160 B,  162 A,  162 B to pierce the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. Thus, the mixing instrument  100  can be handled more easily. 
         [0185]    According to the second embodiment, when the drug holder  114 , the connector  122 , and the liquid holder  118  are fitted together, the drug holder  114 , the connector  122 , and the liquid holder  118  slide against each other and are guided for relative axial movement. Therefore, the first puncture needles  142 A,  142 B and the second puncture needles  144 A,  144 B are capable of piercing the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively, accurately and simply in the axial direction. Therefore, the mixing instrument  100  can be handled more easily. 
         [0186]    According to the second embodiment, when the drug holder  114 , the connector  122 , and the liquid holder  118  are coupled together, the drug holder  114 , the connector  122 , and the liquid holder  118  are locked by the lock mechanism  137 , so that the drug holder  114 , the connector  122 , and the liquid holder  118  can be handled in their entirety as an integrated mixing instrument  100 . Consequently, it is easy to perform the process of shaking the mixing instrument  100  in order to accelerate mixing of the first component and the second component. 
         [0187]    One or both of the two double-ended needles  120 A,  120 B may be constituted in the same manner as the double-ended needle  71  shown in  FIG. 8A , or may be constituted in the same manner as the double-ended needle  90  shown in  FIG. 8B . 
       Third Embodiment 
       [0188]      FIG. 13  is a cross-sectional view of a mixing instrument  200  according to a third embodiment of the present invention. Components of the mixing instrument  200  according to the third embodiment, which have identical or similar functions and advantages to those of the mixing instrument  10  according to the first embodiment, are denoted by identical reference characters, and such features will not be described in detail below. 
         [0189]    The mixing instrument  200  includes a connector  202  that is used in place of, and differs in constitution from the connector  22  of the mixing instrument according to the first embodiment. The connector  202  has a double-ended needle  204  that brings the drug container  12  and the liquid container  16  into fluid communication with each other. The double-ended needle  204  includes a first puncture needle  206  for piercing the first plug  26  and a second puncture needle  208  for piercing the second plug  30 . The double-ended needle  204  is formed integrally with the connector  202 . 
         [0190]    Other constitutive details of the connector  202  are the same as those of the connector  22  of the mixing instrument according to the first embodiment. More specifically, the connector  202  has a partition  46  extending horizontally, a lower side wall  48  extending downwardly from the partition  46 , and an upper side wall  50  extending upwardly from the partition  46 . The first puncture needle  206  is mounted on the lower surface of the partition  46 , whereas the second puncture needle  208  is mounted on the upper surface of the partition  46 . 
         [0191]    The lower side wall  48  surrounds the first puncture needle  206 . The lower side wall  48  has a height (vertical dimension), which is greater than the height of the first puncture needle  206 , so that the distal end (cutting face) of the first puncture needle  206  does not project downwardly from the lower end of the lower side wall  48 . 
         [0192]    The upper side wall  50  surrounds the second puncture needle  208 . The upper side wall  50  has a height, which is greater than the height of the second puncture needle  208 , so that the distal end (cutting face) of the second puncture needle  208  does not project upwardly from the upper side wall  50 . 
         [0193]    The connector  202  can be inserted into the drug holder  14  such that the outer circumferential surface of the upper side wall  50  serves as a sliding surface. More specifically, the connector  202  can slide longitudinally (vertically) along the double-ended needle  204  into fitting engagement with the drug holder  14 . 
         [0194]    The mixing instrument  200  includes a lock mechanism  37 , which is identical in constitution to the lock mechanism  37  of the mixing instrument  10 . The lock mechanism  37  serves to releasably lock the drug holder  14 , the connector  202 , and the liquid holder  18  inseparably together, when the drug holder  14 , the connector  202 , and the liquid holder  18  are fitted together in a relative positional relation, such that the first puncture needle  206  pierces the first plug  26  and the second puncture needle  208  pierces the second plug  30 . 
         [0195]    According to a modification of the lock mechanism  37  shown in  FIG. 13 , the drug holder  14  may have lock members similar to the lock members  38 ,  40 , and the liquid holder  18  may have ledges similar to the ledges  32 ,  34  for engaging with the lock members. 
         [0196]      FIG. 14  is an enlarged cross-sectional view, partially omitted from illustration, showing the double-ended needle  204 , which is formed integrally with the connector  202 , and nearby parts. As shown in  FIG. 14 , the double-ended needle  204  has a lumen  210  (bore) extending longitudinally (axially), and which is open at opposite ends thereof. One of the openings of the lumen  210  opens at a cutting face  212  of the first puncture needle  206 , and the other opening of the lumen  210  opens at a cutting face  214  of the second puncture needle  208 . 
         [0197]    Respective needle point angles θ 1 , θ 2  of the first puncture needle  206  and the second puncture needle  208 , and respective elastic characteristics of the first plug  26  and the second plug  30  are established, such that when the first plug  26  is pressed by the first puncture needle  206  and the second plug  30  is pressed by the second puncture needle  208 , the openings at the opposite ends of the lumen  210  of the double-ended needle  204  are sealed by the first plug  26  and the second plug  30 , respectively. 
         [0198]    The first puncture needle  206  and the second puncture needle  208  may be made of materials, which are the same as the aforementioned materials of the drug holder  14 . 
         [0199]    The first puncture needle  206  and the partition  46  may be formed integrally with each other, or alternatively, may be formed as separate members, which are secured together by adhesive bonding, welding, or the like. Likewise, the second puncture needle  208  and the partition  46  may be formed integrally with each other, or alternatively, may be formed as separate members, which are secured together by adhesive bonding, welding, or the like. For example, the first puncture needle  206  and the second puncture needle  208  may be made of metal, preferably SUS, whereas the connector  202  itself may be integrally molded from a resin material. 
         [0200]    According to the third embodiment, as shown in  FIG. 14 , the first puncture needle  206  and the second puncture needle  208  have respective cutting faces  212 ,  214 , which are shaped as concave surfaces and are curved as viewed in vertical cross section. Typically, with respect to the first puncture needle  206 , the gradient of the cutting face  212  with respect to the axial direction increases progressively from a proximal end portion  216  toward a distal end portion  218  thereof. 
         [0201]    The cutting face  212  of the first puncture needle  206  and the cutting face  214  of the second puncture needle  208  are oriented in one direction with respect to directions (horizontal directions in  FIG. 14 ) perpendicular to the axial direction. 
         [0202]    As shown in  FIG. 14 , the height h 1  in the axial direction of the cutting face  212  of the first puncture needle  206  is smaller than the thickness t 1  (see  FIG. 13 ) of the portion of the first plug  26  that is pierced by the first puncture needle  206 . Similarly, the height h 2  in the axial direction of the cutting face  214  of the second puncture needle  208  is smaller than the thickness t 2  (see  FIG. 13 ) of the portion of the second plug  30  that is pierced by the second puncture needle  208 . The thicknesses t 1 , t 2  of such portions of the first plug  26  and the second plug  30  are preferably in the range from 1 to 4 mm, and more preferably, in the range from 2.0 to 2.5 mm. 
         [0203]      FIG. 15  is an enlarged cross-sectional view, partially omitted from illustration, showing the first puncture needle  206  and nearby parts of the double-ended needle  204  of the mixing instrument  200 . Since the constitution of the first puncture needle  206  and the second puncture needle  208  are basically the same, the shape of the first puncture needle  206  of the double-ended needle  204  will typically be described below. 
         [0204]    According to the third embodiment, as shown in  FIG. 15 , a line segment A extends between the distal end portion  218  and the proximal end portion  216  of the cutting face  212 , and a line B normal to the line segment A extends from a deepest point on the concave surface (the cutting face  212 ). The point of intersection between the line segment A and the line B is positioned closer to the proximal end portion  216  of the cutting face  212  than the midpoint of the line segment A. The distance between the point of intersection and the distal end portion  218  of the cutting face  212  is set to a value, which is in the range of ⅗ to ⅘ the length of the line segment A. In other words, the cutting face (the concave surface)  212  has a curved shape, the concavity of which is formed more deeply near the proximal end portion  216  than near the distal end portion  218 . The center C 2  of the lumen  210  is closer to the proximal end portion  216  of the cutting face  212  than the central line C 1  of the first puncture needle  206 . 
         [0205]    The angle θ 1   a  formed between a line tangential to the distal end portion  218  of the cutting face  212  and the central line C 1  is preferably of a value in the range from 5° to 40°, and more preferably, in the range from 10° to 30°. If the angle θ 1   a  is smaller than 5°, then the mechanical strength of the cutting edge is reduced to such an extent that when the cutting edge attempts to pierce the first plug  26 , the distal end tends to become bent, and it is difficult to pierce the first plug  26 . If the angle θ 1   a  is in excess of 40°, then the cutting edge has an obtuse angle, thus presenting a large penetration resistance when the cutting edge attempts to pierce the first plug  26 , and making the first puncture needle  206  poor in operability. 
         [0206]    The angle θ 1   b  formed between a line tangential to the proximal end portion  216  of the cutting face  212  and the central line C 1  is preferably of a value in the range from 90° to 150°, and more preferably, in the range from 100° to 130°. If the angle θ 1   b  is smaller than 90°, then the lumen  210  extends to the proximal end of the first puncture needle  206 , and the sealing capability at the time that the first puncture needle  206  contacts the first plug  26  is lost. Further, the extending portion of the lumen  210  tends to hollow out the first plug  26 , resulting in coring. If the angle θ 1   b  is in excess of 150°, then when the first puncture needle  206  pierces the first plug  26 , the cutting face  212  does not come into full contact with the first plug  26 , resulting in poor sealing capability. 
         [0207]    In the illustrated mixing instrument  200 , θ 1   a  is set to 30° and θ 1   b  is set to 110°. 
         [0208]    The mixing instrument  200  according to the third embodiment is basically constituted as described above. Operations and advantages of the mixing instrument  200  will be described below. 
         [0209]    As shown in  FIG. 16 , the drug container  12  is held by the drug holder  14 , and is secured in the drug holder  14  by the restraint member  36 . The liquid container  16  also is mounted in the liquid holder  18  and is held by the liquid holder  18 . 
         [0210]    Then, the connector  202 , with the double-ended needle  204  installed therein, is inserted into the drug holder  14  with the first puncture needle  206  being oriented toward the drug container  12 . The liquid holder  18 , with the liquid container  16  mounted therein, is inserted into the connector  202  with the second plug  30  being oriented toward the second puncture needle  208 . 
         [0211]    During the insertion process, as shown in  FIG. 16 , the first puncture needle  206  is pressed against the first plug  26 , and the second puncture needle  208  is pressed against the second plug  30 , whereby the first plug  26  and the second plug  30  are elastically deformed.  FIG. 17  is an enlarged cross-sectional view, partially omitted from illustration, showing the first puncture needle  206 , the first plug  26 , and nearby parts at this time. 
         [0212]    As described above, the respective needle point angles θ 1 , θ 2  of the first puncture needle  206  and the second puncture needle  208 , and the elastic characteristics of the first plug  26  and the second plug  30  are established, such that when the first puncture needle  206  is pressed by the first plug  26  and the second puncture needle  208  is pressed by the second plug  30 , openings in opposite ends of the lumen  210  of the double-ended needle  204  are sealed by the first plug  26  and the second plug  30 , respectively. When the double-ended needle  204  pierces the first plug  26  and the second plug  30 , the first plug  26 , which is pressed by the first puncture needle  206 , and the second plug  30 , which is pressed by the second puncture needle  208 , are elastically deformed, so that the first plug  26  is held in close contact with the cutting face  212  of the first puncture needle  206  and the second plug  30  is held in close contact with the cutting face  214  of the second puncture needle  208 . As a result, openings in opposite ends of the lumen  210  are sealed respectively by the first plug  26  and the second plug  30 . 
         [0213]    According to the double-ended needles of the background art, the needle point angles are relatively small, so as to reduce the resistance that the double-ended needles undergo when the double-ended needles penetrate the plugs. Therefore, the double-ended needles penetrate the plugs easily. According to the double-ended needles of the background art, consequently, the openings in the opposite ends of the lumen cannot be sealed simultaneously by the plugs. 
         [0214]    According to the third embodiment of the present invention, the needle point angles of the first puncture needle  206  and the second puncture needle  208  are greater than in the double-ended needles of the background art, thereby intentionally lowering the forces with which the first puncture needle  206  and the second puncture needle  208  penetrate (pierce) the first plug  26  and the second plug  30 . Therefore, the first plug  26  and the second plug  30  are elastically deformed significantly, so as to seal the openings in the opposite ends of the lumen  210 . 
         [0215]    Whether or not the openings in the opposite ends of the lumen  210  can be sealed by the first plug  26  and the second plug  30  is determined by the forces applied by the first puncture needle  206  and the second puncture needle  208  to penetrate the first plug  26  and the second plug  30  (i.e., the sharpness of the needle points), together with the elastic characteristics, such as hardness and elongation characteristics, of the first plug  26  and the second plug  30 . Therefore, the needle point angles θ 1 , θ 2  of the first puncture needle  206  and the second puncture needle  208  are established in view of the elastic characteristics of the first plug  26  and the second plug  30 . 
         [0216]    According to the third embodiment, the proximal end areas of the cutting faces  212 ,  214 , which are formed as concave surfaces of the first puncture needle  206  and the second puncture needle  208 , function as chins. Since such chins increase the penetration resistance with which the first plug  26  and the second plug  30  are penetrated, when the distal ends of the first puncture needle  206  and the second puncture needle  208  bite into the first plug  26  and the second plug  30 , the chins temporarily bear the first plug  26  and the second plug  30 . Since the openings of the lumen  210  are positioned closer to the proximal end portions (the chins) of the cutting faces  212 ,  214  than the needle central line C 1 , while the chins bear the first plug  26  and the second plug  30 , the openings in the opposite ends of the lumen  210  are sealed simultaneously by the first plug  26  and the second plug  30 . 
         [0217]    When the liquid holder  18  is further pushed toward the drug holder  14  from the state shown in  FIG. 16 , the mixing instrument  200  becomes assembled, as shown in  FIG. 18 . The lock mechanism  37  is easily brought into the aforementioned first state. More specifically, the first engaging portions  38   b ,  40   b  of the arms  38   a ,  40   a  engage with the ledges  32 ,  34 , respectively, of the drug holder  14 , and the second engaging portions  38   c ,  40   c  of the arms  38   a ,  40   a  engage with the ledges  52 ,  54 , respectively, of the connector  22 . In this manner, the lock mechanism  37  operates to limit the mutual positional relation between the drug container  12  and the liquid container  16 , i.e., to prevent the containers  12 ,  16  from unduly moving, thereby reliably maintaining the drug container  12  and the liquid container  16  in fluid communication with each other. 
         [0218]    When the liquid holder  18  is further pushed toward the drug holder  14  from the state shown in  FIG. 18 , and the distance that the first puncture needle  206  bites into the first plug  26  increases to a certain extent, the first plug  26  is no longer capable of withstanding the pressure from the first puncture needle  206 , and the first puncture needle  206  then pierces the first plug  26 . Similarly, when the distance that the second puncture needle  208  bites into the second plug  30  increases to a certain extent, the second plug  30  is no longer capable of withstanding the pressure from the second puncture needle  208 , and the second puncture needle  208  then pierces the second plug  30 . The cutting faces  212 ,  58  of the first puncture needle  206  and the second puncture needle  208  move into the drug container  12  and the liquid container  16 , respectively, whereby the drug container  12  and the liquid container  16  are brought into fluid communication with each other by the double-ended needle  204 . 
         [0219]    Inasmuch as a negative pressure is developed in the drug container  12 , the liquid in the liquid container  16  is attracted to and flows into the drug container  12  through the double-ended needle  204 . Thereafter, in order to mix the drug and the liquid in the drug container  12 , the mixing instrument  200  is shaken several times. The drug in the drug container  12  becomes diluted and dissolved by the liquid that has flowed into the drug container  12 . 
         [0220]    After mixing of the first component and the second component is completed, the arms  38   a ,  40   a  of the lock members  38 ,  40  on the liquid holder  18  are pressed inwardly toward the liquid holder  18 . The first engaging portions  38   b ,  40   b  of the arms  38   a ,  40   a  disengage from the ledges  32 ,  34  of the drug holder  14 , whereas the second engaging portions  38   c ,  40   c  of the arms  38   a ,  40   a  remain in engagement with the ledges  52 ,  54  of the connector  202 . In other words, the lock mechanism  37  is brought into the second state. 
         [0221]    Then, the liquid holder  18  is pulled upwardly. The liquid holder  18 , which holds the liquid container  16  therein, can now be released (removed) from the drug holder  14  together with the connector  22 . Since the projections  38   d ,  40   d  are disposed on outer circumferential surfaces of the arms  38   a ,  40   a , the user finds it easy to pull the liquid holder  18 , because the projections  38   d ,  40   d  function as a slip stop when the arms  38   a ,  40   a  are pressed laterally inward. 
         [0222]    Then, the drug holder  14 , from which the connector  202  has been removed, is vertically inverted. The left and right side walls of the drug holder  14  are pressed inwardly to release the restraint member  36  out of engagement with the drug holder  14 . The drug container  12  is released (drops) from the drug holder  14  together with the restraint member  36 . 
         [0223]    According to the third embodiment, as described above, the needle point angles of the first puncture needle  206  and the second puncture needle  208 , and the elastic characteristics of the first plug  26  and the second plug  30  are established, such that when the first plug  26  is pressed by the first puncture needle  206  and the second plug  30  is pressed by the second puncture needle  208 , the opening of the lumen  210  in the first puncture needle  206  is sealed by the first plug  26 , and the opening in the lumen  210  of the second puncture needle  208  is sealed by the second plug  30 . When the double-ended needle  204  pierces the first plug  26  and the second plug  30 , the first plug  26 , which is pressed by the first puncture needle  206 , and the second plug  30 , which is pressed by the second puncture needle  208 , are initially elastically deformed, so that the openings of the lumens  210  of the first puncture needle  206  and the second puncture needle  208  become sealed by the first plug  26  and the second plug  30 . Thereafter, the first puncture needle  206  and the second puncture needle  208  penetrate the first plug  26  and the second plug  30 , respectively. 
         [0224]    Since the needle point angles of the first puncture needle  206  and the second puncture needle  208 , and the elastic characteristics of the first plug  26  and the second plug  30  are established as described above, openings in opposite ends of the lumen  210  are simultaneously sealed before the first puncture needle  206  and the second puncture needle  208  actually penetrate the first plug  26  and the second plug  30 , respectively. 
         [0225]    Therefore, even if the timing at which the first puncture needle  206  penetrates the first plug  26  differs from the timing at which the second puncture needle  208  penetrates the second plug  30 , negative pressure in the drug container  12  is maintained and liquid is prevented from leaking out. More specifically, even if the first puncture needle  206  penetrates the first plug  26  before the second puncture needle  208  penetrates the second plug  30 , since the opening of the lumen  210  of the second puncture needle  208  is sealed by the second plug  30 , negative pressure in the drug container  12  is maintained. Further, even if the second puncture needle  208  penetrates the second plug  30  before the first puncture needle  206  penetrates the first plug  26 , since the opening of the lumen  210  of the first puncture needle  206  is sealed by the first plug  26 , liquid is prevented from leaking out. 
         [0226]    According to the present invention, therefore, even if the timing at which the first puncture needle  206  penetrates the first plug  26  of the drug container  12  differs from the timing at which the second puncture needle  208  penetrates the second plug  30  of the liquid container  16 , negative pressure in the drug container  12  is maintained and liquid is prevented from leaking out. Accordingly, a mixing instrument  200  is provided, which can be handled easily without causing handling errors. 
         [0227]    According to the third embodiment, each of the respective cutting faces  212 ,  214  of the first puncture needle  206  and the second puncture needle  208  is formed as a curved concave surface, and the point of intersection between a line segment, which extends between the proximal end portion and the distal end portion of each of the cutting faces  212 ,  214 , and the line normal to the line segment, which extends from the deepest point on the concave surface, is positioned closer to the proximal end portion of the cutting face than the midpoint of the line segment. Also, the center of the lumen  210  is closer to the proximal end portion of the cutting face than the central line of each puncture needle. With this arrangement, when the distal ends of the first puncture needle  206  and the second puncture needle  208  bite into the first plug  26  and the second plug  30 , the areas (chins) of the cutting faces  212 ,  214  near the proximal end portions thereof temporarily bear the first plug  26  and the second plug  30 . Since the openings of the lumen  210  are positioned closer to the chins, the openings in the opposite ends of the lumen  210  are reliably and simultaneously sealed. 
         [0228]    According to the third embodiment, when the drug holder  14 , the connector  202 , and the liquid holder  18  are fitted together, the drug holder  14 , the connector  202 , and the liquid holder  18  slide against each other and are guided for relative axial movement. Therefore, the first puncture needle  206  and the second puncture needle  208  can pierce the first plug  26  and the second plug  30 , respectively, accurately and simply in the axial direction. Therefore, the mixing instrument  200  can be handled more easily. 
         [0229]    According to the third embodiment, when the drug holder  14 , the connector  202 , and the liquid holder  18  are coupled together, they are locked by the lock mechanism  37  so that they can be handled in their entirety as the integrated mixing instrument  10 . Consequently, it is easy to perform the process of shaking the mixing instrument  200  to accelerate mixing of the first component and the second component. 
       Fourth Embodiment 
       [0230]      FIG. 19  is an exploded perspective view of a mixing instrument  300  according to a fourth embodiment of the present invention.  FIG. 20  is a cross-sectional view of the mixing instrument  300  according to the fourth embodiment of the present invention. Components of the mixing instrument  300  according to the fourth embodiment, which have identical or similar functions and advantages to those of the mixing instrument  100  according to the second embodiment, are denoted by identical reference characters, and such features will not be described in detail below. 
         [0231]    The mixing instrument  300  includes a connector  302 , which is used in place of and differs in constitution from the connector  122  of the mixing instrument according to the second embodiment. The connector  302  has two integral double-ended needles  304 A,  304 B, which serve to bring the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B into fluid communication with each other. 
         [0232]    The mixing instrument  300  includes a lock mechanism  137 , which is constitutively identical to the lock mechanism  137  of the mixing instrument  100 . The lock mechanism  137  serves to releasably lock the drug holder  114 , the connector  302 , and the liquid holder  118  inseparably together when the drug holder  114 , the connector  302 , and the liquid holder  118  are fitted together in a relative positional relation, such that the first puncture needles  306 A,  306 B pierce the first plugs  126 A,  126 B and the second puncture needles  308 A,  308 B pierce the second plugs  130 A,  130 B. 
         [0233]    According to a modification of the lock mechanism  137  shown in  FIG. 19 , lock members, which are similar to the lock members  138 ,  140 , may be provided on the drug holder  114 , and ledges, which are similar to the ledges  132 ,  134  for engaging the lock members, may be provided on the liquid holder  118 . 
         [0234]    As shown in  FIGS. 19 and 20 , the two double-ended needles  304 A,  304 B have respective first puncture needles  306 A,  306 B for piercing the first plugs  126 A,  126 B, respectively, and respective second puncture needles  308 A,  308 B for piercing the second plugs  130 A,  130 B, respectively. The two double-ended needles  304 A,  304 B are joined together integrally through the connector  302 . 
         [0235]      FIG. 21  is an enlarged cross-sectional view, partially omitted from illustration, showing the pair of double-ended needles  304 A,  304 B and nearby parts. The double-ended needles  304 A,  304 B have respective lumens (bores)  310 A,  310 B extending longitudinally (axially) therethrough, and which are open at opposite ends thereof. One of the openings of the lumens  310 A,  310 B opens into the cutting faces  312 A,  312 B of the first puncture needles  306 A,  306 B, whereas the other opening opens into the cutting faces  314 A,  314 B of the second puncture needles  308 A,  308 B. 
         [0236]    Respective needle point angles θ 1 A, θ 1 B, θ 2 A, θ 2 B of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B, and respective elastic characteristics of the first plugs  126 A,  126 B and the second plugs  130 A,  130 B are established, such that when the first plugs  126 A,  126 B are pressed by the first puncture needles  306 A,  306 B and the second plugs  130 A,  130 B are pressed by the second puncture needles  308 A,  308 B, the openings in opposite ends of the lumens  310 A,  310 B of the double-ended needles  304 A,  304 B are sealed by the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively. 
         [0237]    The first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B may be made of materials, which are the same as the aforementioned materials of the drug containers  112 A,  112 B. 
         [0238]    The first puncture needles  306 A,  306 B and the partition  146  may be formed integrally with each other, or alternatively, may be separate members, which are secured together by adhesive bonding, welding, or the like. Similarly, the second puncture needles  308 A,  308 B and the partition  146  may be formed integrally with each other, or alternatively, may be separate members, which are secured together by adhesive bonding, welding, or the like. For example, the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B may be made of metal, preferably SUS, whereas the connector  302  itself may be integrally molded from a resin material. 
         [0239]    According to the third embodiment, as shown in  FIG. 21 , the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B have respective cutting faces  312 A,  312 B,  314 A,  314 B, which are shaped as concave surfaces and are curved as viewed in vertical cross section. 
         [0240]    In one of the double-ended needles  304 A, the cutting face  312 A of the first puncture needle  306 A and the cutting face  314 A of the second puncture needle  308 A face in the same direction (i.e., the leftward direction shown in  FIG. 20 ), in a direction perpendicular to the axial direction. In the other double-ended needle  304 B, the cutting face  312 B of the first puncture needle  306 B and the cutting face  314 B of the second puncture needle  308 B face in the same direction (i.e., the rightward direction shown in  FIG. 21 ), in a direction perpendicular to the axial direction. The double-ended needle  304 A and the double-ended needle  304 B face away from each other in respective directions in which the double-ended needle  304 A and the double-ended needle  304 B are spaced from each other (i.e., in leftward and rightward directions as shown in  FIG. 20 ). 
         [0241]    According to a modification of the fourth embodiment, the double-ended needles  304 A,  304 B shown in  FIG. 21  may be inverted 180° about central axes thereof. More specifically, the cutting face  312 A of the first puncture needle  306 A and the cutting face  312 B of the first puncture needle  306 B may face toward each other, and the cutting face  314 A of the second puncture needle  308 A and the cutting face  314 B of the second puncture needle  308 B may face toward each other. 
         [0242]    As shown in  FIG. 21 , in the double-ended needle  304 A, the height h 1 A in the axial direction of the cutting face  312 A of the first puncture needle  306 A is smaller than the thickness t 1 A (see  FIG. 20 ) of the portion of the first plug  126 A that is pierced by the first puncture needle  306 A. Further, the height h 12  in the axial direction of the cutting face  314 A of the second puncture needle  308 A is smaller than the thickness t 2 A (see  FIG. 20 ) of the portion of the second plug  130 A that is pierced by the second puncture needle  308 A. The thicknesses t 1 A, t 2 A of the first plug  126 A and the second plug  130 A should preferably be in the range from 1 to 4 mm, and more preferably, in the range from 2.0 to 2.5 mm. 
         [0243]    In the other double-ended needle  304 B, the relationship between the height in the axial direction of the cutting face  312 B of the first puncture needle  306 B and the thickness of the portion of the first plug  126 B that is pierced by the first puncture needle  306 B, and the relationship between the height in the axial direction of the cutting face  314 B of the second puncture needle  308 B and the thickness of the portion of the second plug  130 B that is pierced by the second puncture needle  308 B are the same as in the double-ended needle  304 A. 
         [0244]    According to the fourth embodiment, as with the third embodiment (see  FIG. 4 ), the point of intersection between the line segment that extends between the distal end portion  318  of the cutting face  312 A and the proximal end portion  316  thereof, and the line normal to the line segment, which extends from the deepest point on the concave surface (cutting face), is positioned closer to the proximal end portion of the cutting face than the midpoint of the line segment. Also, the center of the lumen  310 A is closer to the proximal end portion  316  of the cutting face  312 A than the central line of the puncture needle. In other words, the cutting face (concave surface)  312 A is more deeply concave near the proximal end portion  316  of the cutting face  312 A than near the distal end portion  318  thereof. The first puncture needle  306 B and the second puncture needle  308 B of the double-ended needle  304 B are similar in shape to the first puncture needle  306 A of the double-ended needle  304 A. 
         [0245]    The connector  302  has a partition  146  extending horizontally, a lower side wall  148  extending downwardly from the partition  146 , and an upper side wall  150  extending upwardly from the partition  146 . The two first puncture needles  306 A,  306 B are mounted on the lower surface of the partition  146 , whereas the two second puncture needles  308 A,  308 B are mounted on the upper surface of the partition  146 . The connector  302  may be made of materials, which are the same as the aforementioned materials of the drug holder  114 . 
         [0246]    The lower side wall  148  surrounds the first puncture needles  306 A,  306 B in their entirety. The lower side wall  148  has a height (vertical dimension), which is greater than the height of the first puncture needles  306 A,  306 B, so that the distal ends (cutting faces) of the two first puncture needles  306 A,  306 B do not project downwardly from the lower end of the lower side wall  148 . 
         [0247]    The upper side wall  150  surrounds the second puncture needles  308 A,  308 B in their entirety. The upper side wall  150  has a height (vertical dimension), which is greater than the height of the second puncture needles  308 A,  308 B, so that the distal ends (cutting faces) of the two second puncture needles  308 A,  308 B do not project upwardly from the upper side wall  150 . The upper side wall  150  has ledges  152 ,  154  projecting horizontally outwardly from the left and right sides of the upper end thereof. The ledges  152 ,  154  have respective holes  152   a ,  154   a  formed vertically therethrough. 
         [0248]    The connector  302  can be inserted into the drug holder  114 , with the outer circumferential surface of the upper side wall  150  thereof serving as a sliding surface. More specifically, the connector  302  can move longitudinally (vertically) along the double-ended needles  304 A,  304 B with respect to the drug holder  114 . 
         [0249]    The liquid holder  118  can be inserted into the inside of the upper side wall  150  of the connector  302 , with the outer circumferential surface of the lower end portion thereof serving as a sliding surface. More specifically, the liquid holder  118  can move longitudinally along the double-ended needles  304 A,  304 B with respect to the connector  302 . 
         [0250]    The mixing instrument  300  according to the fourth embodiment is basically constituted as described above. Operations and advantages of the mixing instrument  300  will be described below. 
         [0251]    As shown in  FIG. 20 , the drug containers  112 A,  112 B are stored in the drug holder  114  and secured to the drug holder  114  by the restraint member  136 . The liquid containers  116 A,  116 B are mounted in the liquid holder  118  and held by the liquid holder  118 . 
         [0252]    Then, the connector  302 , with the two double-ended needles  304 A,  304 B installed therein, is inserted into the drug holder  114 , such that the two first puncture needles  306 A,  306 B are oriented toward the drug containers  112 A,  112 B. Further, the liquid holder  118 , with the two liquid containers  116 A,  116 B mounted therein, is inserted into the connector  302 , such that the second plugs  130 A,  130 B are oriented toward the second puncture needles  308 A,  308 B. 
         [0253]    During the insertion process, as shown in  FIG. 22 , the first puncture needles  306 A,  306 B are pressed against the first plugs  126 A,  126 B, and the second puncture needles  308 A,  308 B are pressed against the second plugs  130 A,  130 B. Thus, the first plugs  126 A,  126 B and the second plugs  130 A,  130 B are elastically deformed. At this time, the first plugs  126 A,  126 B and the second plugs  130 A,  130 B are elastically deformed significantly, as with the first plug  26  (see  FIG. 17 ) according to the third embodiment. 
         [0254]    As described above, respective needle point angles θ 1 A, θ 2 A, θ 3 A, θ 4 A of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B, and respective elastic characteristics of the first plugs  126 A,  126 B and the second plugs  130 A,  130 B are established, such that when the first puncture needles  306 A,  306 B are pressed against the first plugs  126 A,  126 B and the second puncture needles  308 A,  308 B are pressed against the second plugs  130 A,  130 B, openings in opposite ends of the lumens  310 A,  310 B of the double-ended needles  304 A,  304 B are sealed by the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively. In the illustrated embodiment, θ 1 A to θ 4 A are set to 30°, and θ 1 B to θ 4 B are set to 130°. 
         [0255]    When the pair of double-ended needles  304 A,  304 B pierce the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, the first plugs  126 A,  126 B, which are pressed by the first puncture needles  306 A,  306 B, and the second plugs  130 A,  130 B, which are pressed by the second puncture needles  308 A,  308 B, are elastically deformed initially, so that the first plugs  126 A,  126 B are held in close contact with the cutting faces  312 A,  312 B of the first puncture needles  306 A,  306 B, and the second plugs  130 A,  130 B are held in close contact with the cutting faces  314 A,  314 B of the second puncture needles  308 A,  308 B. As a result, openings in opposite ends of the lumens  310 A,  310 B are sealed respectively by the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. 
         [0256]    With the double-ended needles of the background art, the needle point angles are relatively small in order to reduce the resistance that the double-ended needles undergo when they penetrate the plugs. Therefore, the double-ended needles can penetrate the plugs easily. According to the double-ended needles of the background art, consequently, openings in opposite ends of the lumen cannot be simultaneously sealed by the plugs. 
         [0257]    According to the fourth embodiment of the present invention, the needle point angles of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B are greater than those in the double-ended needles of the background art, thereby intentionally lowering the forces with which the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B penetrate (pierce) the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. Therefore, the first plugs  126 A,  126 B and the second plugs  130 A,  130 B are elastically deformed significantly, so as to seal the openings in the opposite ends of the lumens. 
         [0258]    Whether or not the openings in the opposite ends of the lumens  310 A,  310 B can be sealed by the first plugs  126 A,  126 B and the second plugs  130 A,  130 B is determined by the forces applied by the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B to penetrate the first plugs  126 A,  126 B and the second plugs  130 A,  130 B (i.e., the sharpness of the needle points), together with elastic characteristics, such as hardness and elongation characteristics, of the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. Therefore, the needle point angles of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B are established in view of the elastic characteristics of the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. 
         [0259]    According to the fourth embodiment, the proximal end areas of the cutting faces  312 A,  312 B,  314 A,  314 B, which are formed as concave surfaces, of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B function as chins. Since such chins increase the penetration resistance with which the first plugs  126 A,  126 B and the second plugs  130 A,  130 B are penetrated when the distal ends of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B bite into the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, the chins temporarily bear the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. Since the openings of the lumens  310 A,  310 B are positioned closer to the proximal end portions (the chins) of the cutting faces than the central lines of the double-ended needles  304 A,  304 B, while the chins bear the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, the openings in the opposite ends of the lumens are simultaneously sealed by the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. 
         [0260]    When the liquid holder  118  is further pushed toward the drug holders  114  from the state shown in  FIG. 22 , the mixing instrument  300  is assembled together, as shown in  FIG. 23 . The lock mechanism  137  is easily brought into the first state, as described above. More specifically, the first engaging portions  138   b ,  140   b  of the arms  138   a ,  140   a  engage with the respective ledges  132 ,  134  of the drug holder  114 , and the second engaging portions  138   c ,  140   c  of the arms  138   a ,  140   a  engage the respective ledges  152 ,  154  of the connector  302 . The lock mechanism  137  thus operates to limit the mutual positional relation between the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B, i.e., to prevent the containers  112 A,  112 B,  116 A,  116 B from unduly moving, thereby reliably maintaining the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B in fluid communication with each other. 
         [0261]    When the liquid holder  118  is further pushed toward the drug holder  114  from the state shown in  FIG. 22 , the distance at which the first puncture needles  306 A,  306 B bite into the first plugs  126 A,  126 B increases to a certain extent, and the first plugs  126 A,  126 B are no longer capable of withstanding the pressure from the first puncture needles  306 A,  306 B, which then pierce the first plugs  126 A,  126 B. Similarly, when the distance at which the second puncture needles  308 A,  308 B bite into the second plugs  130 A,  130 B increases to a certain extent, the second plugs  130 A,  130 B are no longer capable of withstanding the pressure from the second puncture needles  308 A,  308 B, which then pierce the second plugs  130 A,  130 B. The cutting faces of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B move respectively into the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B. At this time, the drug containers  112 A,  112 B and the liquid containers  116 A,  116 B are brought into fluid communication with each other through the double-ended needles  304 A,  304 B. 
         [0262]    Inasmuch as a negative pressure is developed in the two drug containers  112 A,  112 B, the liquid in the liquid containers  116 A,  116 B is attracted to and flows into the drug containers  112 A,  112 B through the two double-ended needles  304 A,  304 B. Thereafter, the mixing instrument  300  is shaken several times. At this time, the drugs in the drug containers  112 A,  112 B become diluted and dissolved by the liquids, which have flowed into the drug containers  112 A,  112 B. 
         [0263]    After mixing of the drugs and the liquids is completed, the arms  138   a ,  140   a  of the lock members  138 ,  140  on the liquid holder  118  are pressed inwardly toward the liquid holder  118 . The first engaging portions  138   b ,  140   b  of the arms  138   a ,  140   a  disengage from the ledges  132 ,  134  of the drug holder  114 , whereas the second engaging portions  138   c ,  140   c  of the arms  138   a ,  140   a  remain in engagement with the ledges  152 ,  154  of the connector  122 . In other words, the lock mechanism  137  is brought into the second state. 
         [0264]    Then, the liquid holder  118  is pulled upwardly. The liquid holder  118 , which holds the liquid containers  116 A,  116 B therein, can be released (removed) from the drug holder  114  together with the connector  302 . Since the projections  138   d ,  140   d  are disposed on the arms  138   a ,  140   a , the user finds it easy to pull the liquid holder  118  due to the fact that the projections  138   d ,  140   d  function as a slip stop. 
         [0265]    Then, the drug holder  114 , from which the connector  302  has been removed, is vertically inverted. The left and right side walls of the drug holder  114  are pressed inwardly to cause the engaging protrusion  141  of the restraint member  136  to become disengaged from the engaging recess  143  of the drug holder  114 . At this time, the drug containers  112 A,  112 B are released (drop) from the drug holder  114  together with the restraint member  136 . 
         [0266]    According to the fourth embodiment, as described above, the double-ended needle  304 A and the double-ended needle  304 B face away from each other in respective directions in which the double-ended needle  304 A and the double-ended needle  304 B are spaced from each other. Consequently, when the double-ended needles  304 A,  304 B pierce the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively, forces acting horizontally on the double-ended needles  304 A,  304 B cancel each other out. Therefore, sliding resistance between the connector  302  and the drug holder  114  is prevented from increasing at the time that the connector  302  is inserted into the drug holder  114 . 
         [0267]    Further, according to the fourth embodiment, as described above, the needle point angles of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B, and elastic characteristics of the first plugs  126 A,  126 B and the second plugs  130 A,  130 B are established, such that when the first plugs  126 A,  126 B are pressed against the first puncture needles  306 A,  306 B, and the second plugs  130 A,  130 B are pressed against the second puncture needles  308 A,  308 B, the openings of the lumens  310 A,  310 B of the first puncture needles  306 A,  306 B are sealed by the first plugs  126 A,  126 B, respectively, and the openings of the lumens  310 A,  310 B of the second puncture needles  308 A,  308 B are sealed by the second plugs  130 A,  130 B, respectively. When the double-ended needles  304 A,  304 B pierce the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, the first plugs  126 A,  126 B, which are pressed by the first puncture needles  306 A,  306 B, and the second plugs  130 A,  130 B, which are pressed by the second puncture needles  308 A,  308 B, are elastically deformed initially, so that the openings of the lumens  310 A,  310 B of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B are sealed respectively by the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. Thereafter, the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B pierce the first plug  26  and the second plugs  130 A,  130 B, respectively. In other words, the openings at opposite ends of the lumens  310 A,  310 B are simultaneously sealed before the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B penetrate through the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively. 
         [0268]    Consequently, even if the first puncture needles  306 A,  306 B penetrate the first plugs  126 A,  126 B before the second puncture needles  308 A,  308 B have penetrated the second plugs  130 A,  130 B, since the openings of the lumens of the second puncture needles  308 A,  308 B are sealed by the second plugs  130 A,  130 B, negative pressure in the drug containers  112 A,  112 B can be maintained. Further, even if the second puncture needles  308 A,  308 B penetrate the second plugs  130 A,  130 B before the first puncture needles  306 A,  306 B have penetrated the first plugs  126 A,  126 B, since the openings of the lumens of the first puncture needles  306 A,  306 B are sealed by the first plugs  126 A,  126 B, liquids are prevented from leaking out. 
         [0269]    Consequently, negative pressure in the drug containers  112 A,  112 B is maintained, and the first components are prevented from leaking out, even if the timing at which the first puncture needles  306 A,  306 B penetrate the first plugs  126 A,  126 B differs from the timing at which the second puncture needles  308 A,  308 B penetrate the second plugs  130 A,  130 B. Accordingly, a mixing instrument  300  is provided, which can be handled easily without causing handling errors. 
         [0270]    According to the fourth embodiment, the cutting faces of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B are formed as concave surfaces, and the point of intersection between a line segment that extends between the proximal end portion of each of the cutting faces and the distal end portion thereof, and the line normal to the line segment, which extends from the deepest point on the concave surface, is positioned closer to the proximal end portion of the cutting face than the midpoint of the line segment. Also, the center of the lumen is closer to the proximal end portion of the cutting face than the central line of each puncture needle. With this arrangement, when the distal ends of the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B bite into the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, the proximal end areas (i.e., chins) of the cutting faces temporarily bear the first plugs  126 A,  126 B and the second plugs  130 A,  130 B. Since the openings at the opposite ends of the lumens  310 A,  310 B are positioned closer to the chins, the openings at the opposite ends of the lumens  310 A,  310 B are reliably and simultaneously sealed. 
         [0271]    According to the fourth embodiment, when the drug holder  114 , the connector  302 , and the liquid holder  118  are fitted together, the components slide against each other and are guided for relative axial movement. Therefore, the first puncture needles  306 A,  306 B and the second puncture needles  308 A,  308 B are capable of piercing the first plugs  126 A,  126 B and the second plugs  130 A,  130 B, respectively, accurately and simply in the axial direction. Therefore, the mixing instrument  300  can be handled more easily. 
         [0272]    According to the fourth embodiment, when the drug holder  114 , the connector  302 , and the liquid holder  118  are coupled together, the drug holder  114 , the connector  302 , and the liquid holder  118  become locked by the lock mechanism  37 , so that they can be handled in their entirety as an integrated mixing instrument  300 . Consequently, it is easy to perform the process of shaking the mixing instrument  300  in order to accelerate mixing of the first component and the second component. 
         [0273]    The present invention is not limited to the above arrangements, but various other arrangements may be adopted based on the content of the present description.