Abstract:
In various embodiments, a surgical system is disclosed. The surgical system comprises a medicament and a surgical instrument comprising a plurality of staples, a cavity configured to store the medicament, a delivery passage configured to convey the medicament from the cavity to tissue, and a firing system. The firing system comprises a movable member and a firing member, wherein the firing system is configured to cooperatively move the movable member and the firing member to concurrently fire the plurality of staples and deliver at least a portion of the medicament to the tissue owing to advancement of the firing member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application claiming priority under 35 U.S.C. §120 from U.S. patent application Ser. No. 13/544,128, entitled SURGICAL STAPLING INSTRUMENT HAVING A MEDICAL SUBSTANCE DISPENSER, filed on Jul. 9, 2012, which issued as U.S. Pat. No. 8,517,244 on Aug. 27, 2013, which is a continuation application claiming priority under 35 U.S.C. §120 from U.S. patent application Ser. No. 12/696,397, entitled SURGICAL STAPLING INSTRUMENT HAVING A MEDICAL SUBSTANCE DISPENSER, filed on Jan. 29, 2010, which issued as U.S. Pat. No. 8,215,531 on Jul. 10, 2012, which is a continuation-in-part application claiming priority under 35 U.S.C. §120 from U.S. patent application Ser. No. 11/141,753, entitled SURGICAL STAPLING INSTRUMENT HAVING AN ELECTROACTIVE POLYMER ACTUATED MEDICAL SUBSTANCE DISPENSER, filed on Jun. 1, 2005, which issued as U.S. Pat. No. 8,905,977 on Dec. 9, 2014, which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Ser. No. 60/591,694, entitled SURGICAL INSTRUMENT INCORPORATING AN ELECTRICALLY ACTUATED ARTICULATION MECHANISM, filed Jul. 28, 2004, the entire disclosures of which are incorporated by reference herein. U.S. patent application Ser. No. 13/544,128, entitled SURGICAL STAPLING INSTRUMENT HAVING A MEDICAL SUBSTANCE DISPENSER, filed on Jul. 9, 2012, which issued as U.S. Pat. No. 8,517,244 on Aug. 27, 2013, is also a continuation application claiming priority under 35 U.S.C. §120 from U.S. patent application Ser. No. 12/696,397, entitled SURGICAL STAPLING INSTRUMENT HAVING A MEDICAL SUBSTANCE DISPENSER, filed on Jan. 29, 2010, which issued as U.S. Pat. No. 8,215,531 on Jul. 10, 2012, which is a continuation-in-part application claiming priority under 35 U.S.C. §120 from U.S. patent application Ser. No. 11/731,521, entitled DISPOSABLE LOADING UNIT AND SURGICAL INSTRUMENTS INCLUDING SAME, filed on Mar. 30, 2007, now U.S. Patent Publication No. 2007/0170225, which is a continuation application of U.S. patent application Ser. No. 11/271,234, entitled DISPOSABLE LOADING UNIT AND SURGICAL INSTRUMENTS INCLUDING SAME, filed on Nov. 10, 2005, which issued as U.S. Pat. No. 7,354,447 on Apr. 8, 2008, the entire disclosures of which are hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     The present application relates in general to surgical stapler instruments that are capable of applying lines of staples to tissue while cutting the tissue between those staple lines and, more particularly, to improvements relating to stapler instruments and improvements in processes for forming various components of such stapler instruments. This application also discloses devices that are related, generally and in various embodiments, to a disposable loading unit configured for connection to a reusable surgical instrument, and to surgical instruments that include a disposable loading unit. 
     Surgical instruments that are utilized to concurrently make longitudinal incisions in tissue and apply lines of staples on opposing sides of the incisions are known in the art. The tissue may include, for example, human tissue, animal tissue, membranes, or other organic substances. Such surgical instruments commonly include a pair of opposing jaw members that cooperate to grasp or clamp the tissue therebetween and a cutting surface that makes the incision. When employed in endoscopic or laparoscopic applications, the opposing jaw members are capable of passing through a cannula passageway. One of the jaw members typically supports a staple cartridge having at least two laterally spaced rows of staples and pushers aligned with the staples. The other jaw member is movable between an open position and a closed position, and defines an anvil having staple-forming pockets correspondingly aligned with the rows of staples in the staple cartridge. Such instruments may also include a wedge that, when driven, sequentially contacts the pushers to effect the firing of the staples toward the anvil and through the tissue. 
     An example of a surgical stapler suitable for endoscopic applications, described in U.S. Pat. No. 5,465,895, advantageously provides distinct closing and firing actions. Thereby, a clinician is able to close the jaw members upon tissue to position the tissue prior to firing. Once the clinician has determined that the jaw members are properly gripping tissue, the clinician can then fire the surgical stapler, thereby severing and stapling the tissue. The simultaneous severing and stapling avoids complications that may arise when performing such actions sequentially with different surgical tools that respectively only sever or staple. 
     However, the trauma caused to the tissue with such actions can be significant. In general, the delivery of sufficient amounts of medical agents to the site of the traumatized tissue promotes the proper sealing of the incision, reduces the possibility of infection, and/or significantly improves the healing process. The application of medical agents to the site of the traumatized tissue is often accomplished by means other than the surgical instrument that makes the incision and applies the staples. Such means generally increase the complexity and cost associated with the procedure. However, such means are often necessary because many of the surgical instruments utilized to concurrently make the incision and apply the staples are not configured to store and deliver sufficient amounts of medical agents to the site of the traumatized tissue, and the delivery of some medical agents to the site of the traumatized tissue via the surgical instrument would render the surgical instrument unsuitable for reuse. 
     The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope. 
     SUMMARY 
     In various embodiments, an end effector for use with a surgical instrument is provided. The end effector comprises a plurality of staples, an agent reservoir comprising a medical agent, a dispensing passage configured to convey the medical agent from the agent reservoir to tissue, and a firing system. The firing system comprises a cutting member, a movable member, and a firing member, wherein the firing system is configured to cooperatively move the movable member and the firing member to simultaneously fire the plurality of staples and dispense at least a portion of the medical agent near the cutting member owing to advancement of the firing member. 
     In various embodiments, a firing system for use with a surgical instrument is provided. The firing system comprises a plurality of fasteners, an agent cavity comprising a medical agent, a delivery passage configured to convey the medical agent from the agent cavity to tissue, and a firing system. The firing system comprises a cutting member, a movable member, and a firing member, wherein the firing system is configured to cooperatively move the movable member and the firing member to simultaneously fire the plurality of fasteners and deliver at least a portion of the medical agent to the tissue owing to advancement of the firing member. 
     In various embodiments, a surgical instrument is provided. The surgical instrument comprises a shaft and an end effector extending distally from the shaft. The end effector comprises a plurality of staples, an agent reservoir comprising a medical agent, a dispensing passage configured to convey the medical agent from the agent reservoir to tissue, and a firing system. The firing system comprises a cutting member, a movable member, and a firing member, wherein the firing system is configured to cooperatively move the movable member and the firing member to simultaneously fire the plurality of staples and dispense at least a portion of the medical agent adjacent the cutting member as a result of the firing of the firing member. 
     In various embodiments, a surgical system is provided. The surgical system comprises a medicament and a surgical instrument comprising a plurality of staples, a cavity configured to store the medicament, a delivery passage configured to convey the medicament from the cavity to tissue, and a firing system. The firing system comprises a movable member and a firing member, wherein the firing system is configured to cooperatively move the movable member and the firing member to concurrently fire the plurality of staples and deliver at least a portion of the medicament to the tissue owing to advancement of the firing member. 
     In various embodiments, a surgical instrument is provided. The surgical instrument comprises a shaft and an end effector extending distally from the shaft. The end effector comprises a plurality of fasteners, an agent reservoir configured to store a medicament, a dispensing passage configured to convey the medicament from the agent reservoir to tissue, and a firing system. The firing system comprises a cutting member, a movable member, and a firing member, wherein the firing system is configured to cooperatively move the movable member and the firing member to concurrently fire the plurality of fasteners and dispense at least a portion of the medicament adjacent the cutting member as a result of the firing of the firing member. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The novel features of the embodiments described herein are set forth with particularity in the appended claims. The embodiments, however, both as to organization and methods of operation may be better understood by reference to the following description, taken in conjunction with the accompanying drawings as follows. 
         FIG. 1  is a perspective view of a surgical stapling and severing instrument having a fluid actuated upper jaw (anvil) in an open position and an electroactive polymer (EAP) medical substance dispensing shaft. 
         FIG. 2  is a disassembled perspective view of an implement portion of the surgical stapling and severing instrument of  FIG. 1 . 
         FIG. 3  is left side view in a elevation of the implement portion of the surgical stapling and severing instrument of  FIG. 1  taken in cross section generally through a longitudinal axis and passing through an offset EAP syringe and receptacle that is in fluid communication with a dispensing groove in an E-beam firing bar. 
         FIG. 4  is a left side detail view in elevation of a distal portion of the implement portion of the surgical stapling and severing instrument of  FIG. 1  taken in cross section generally through the longitudinal axis thereof but showing a laterally offset fluid bladder actuator opening the anvil. 
         FIG. 5  is a left side detail view of an E-beam firing bar incorporating medical substance ducting. 
         FIG. 6  is a left side detail view in elevation of the distal portion of the implement portion of the surgical stapling and severing instrument of  FIG. 4  taken in cross section generally through the longitudinal axis thereof with the anvil closed. 
         FIG. 7  is a left side detail view of the E-beam firing bar of  FIG. 6 . 
         FIG. 8  is a top detail view of a joined portion of a lower jaw (staple channel) of the end effector and elongate shaft taken in cross section through the lines  8 - 8  depicting guidance to the E-beam firing bar. 
         FIG. 9  is a front view of a firing bar guide of the implement portion of the surgical stapling and severing instrument of  FIG. 2 . 
         FIG. 10  is a left side view of the firing bar guide of  FIG. 9  taken in cross section along lines  9 - 9 . 
         FIG. 11  is a front view in elevation of the elongate shaft of the surgical stapling and severing instrument of  FIG. 3  taken along lines  11 - 11  taken through a distal end of the EAP medical substance syringe. 
         FIG. 12  is a left side view of the EAP medical substance syringe of  FIG. 11 . 
         FIG. 13  is a left side view of the implement portion of the surgical stapling and severing instrument of  FIG. 1  partially cut away to show proximal mountings for the EAP medical substance syringe. 
         FIG. 14  is a left side detail view of the EAP medical substance syringe and receptacle of the elongate shaft of the surgical stapling and severing instrument of  FIG. 13 . 
         FIG. 15  is a top view of the firing bar of the surgical stapling and severing instrument of  FIG. 2 . 
         FIG. 16  is a left side view of a laminate firing bar showing an internal fluid path in phantom for the surgical stapling and severing instrument of  FIG. 1 . 
         FIG. 17  is a left side detail view of an alternate E-beam showing an internal fluid path in phantom showing an internal fluid path in phantom. 
         FIG. 18  is a front view in elevation of the laminate firing bar of  FIG. 15  taken in cross section along line  18 - 18  through a proximal open groove of a fluid path. 
         FIGS. 19-20  illustrate various embodiments of a disposable loading unit. 
         FIG. 21  illustrates various embodiments of an agent cartridge. 
         FIG. 22  illustrates various embodiments of a disposable loading unit. 
         FIG. 23  illustrates various embodiments of a disposable loading unit. 
         FIG. 24  illustrates various embodiments of a disposable loading unit. 
         FIG. 25  illustrates various embodiments of a disposable loading unit. 
         FIG. 26  illustrates various embodiments of a disposable loading unit. 
         FIG. 27  illustrates various embodiments of a disposable loading unit. 
         FIG. 28  illustrates various embodiments of a disposable loading unit. 
         FIG. 29  illustrates various embodiments of a disposable loading unit. 
         FIG. 30  illustrates various embodiments of a disposable loading unit. 
         FIG. 31  illustrates various embodiments of a disposable loading unit. 
         FIG. 32  illustrates various embodiments of a disposable loading unit. 
         FIG. 33  illustrates various embodiments of a surgical instrument. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the figures and descriptions of the disclosed embodiments have been simplified to illustrate elements that are relevant for a clear understanding of the disclosed embodiments, while eliminating, for purposes of clarity, other elements. Those of ordinary skill in the art will recognize, however, that these and other elements may be desirable. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the disclosed embodiments, a discussion of such elements is not provided herein. 
     Certain embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting embodiments and that the scope of these embodiments is defined solely by the claims. The features illustrated or described in connection with one embodiment may be combined with the features of other embodiments. Further, where an ordering of steps in a process is indicated, such ordering may be rearranged or the steps may be carried out contemporaneously as desired unless illogical or the listed order is explicitly required. Such modifications and variations are intended to be included within the scope of the appended claims. 
     Also, in the following description, it is to be understood that terms such as “forward,” “rearward,” “front,” “back,” “right,” “left,” “over,” “under,” “top,” “bottom,” “upwardly,” “downwardly,” “proximally,” “distally,” and the like are words of convenience and are not to be construed as limiting terms. The description below is for the purpose of describing various embodiments and is not intended to limit the appended claims. 
     Turning to the drawings, wherein like numerals denote like components throughout the several views, in  FIGS. 1-2 , a surgical stapling and severing instrument  10  that is capable of practicing the unique benefits of at least one embodiment, including both fluid actuation (e.g., opening, closing/clamping) of an upper jaw (anvil)  12  of an end effector  14  as well as dispensing a medical substance onto tissue as severed. Fluid actuation of the end effector  14  provides a range of design options that avoid some design limitations of traditional mechanical linkages. For example, instances of binding or component failure may be avoided. Further, dispensing liquids onto severed tissue allows for a range of advantageous therapeutic treatments to be applied, such as the application of anesthetics, adhesives, cauterizing substances, antibiotics, coagulant, etc. 
     With particular reference to  FIG. 2 , the surgical stapling and severing instrument  10  includes an implement portion  16  formed by an elongate shaft  18  and the end effector  14 , depicted as a stapling assembly  20 . The surgical stapling and severing instrument  10  also includes a handle  22  ( FIG. 1 ) attached proximally to the shaft  18 . The handle  22  remains external to the patient as the implement portion  16  is inserted through a surgical opening, or especially a cannula of a trocar that forms a pneumoperitoneum for performing a minimally invasive surgical procedure. 
     Left and right fluid bladders (lift bags)  24 ,  26  are supported within an aft portion  28  of a staple channel  30 . The anvil  12  includes a pair of inwardly directed lateral pivot pins  32 ,  34  that pivotally engage outwardly open lateral pivot recesses  36 ,  38  formed in the staple channel  30  distal to the aft portion  28 . The anvil  12  includes a proximally directed lever tray  40  that projects into the aft portion  28  of the staple channel  30  overtop and in contact with the fluid bladders (lift bags)  24 ,  26  such that filling the fluid bladders  24 ,  26  causes a distal clamping section  41  of the anvil  12  to pivot like a teeter-totter toward a staple cartridge  42  held in a distal portion  44  of the staple channel  30 . Evacuation and collapse of the fluid bladders  24 ,  26 , or some other resilient feature of the end effector  14 , causes the anvil  12  to open. Left and right fluid conduits  46 ,  48  communicate respectively with the left and right fluid bladders  24 ,  26  to bi-directionally transfer fluid for actuation. It should be appreciated that applications consistent with the present embodiment may include a mechanical actuation in the handle  22  (e.g., closure trigger) (not shown) wherein the user depresses a control that causes closure and clamping of the end effector  12 . 
     It will be appreciated that the terms “proximal” and “distal” are used herein with reference to a clinician gripping a handle of an instrument. Thus, the staple applying assembly  20  is distal with respect to the more proximal handle  22 . It will be further appreciated that, for convenience and clarity, spatial terms such as “vertical” and “horizontal” are used herein with respect to the drawings. However, surgical instruments are used in many orientations and positions, and these terms are not intended to be limiting and absolute. 
     With particular reference to  FIG. 2 , the elongate shaft  18  includes a frame  50  whose proximal end is rotatably engaged to the handle  22  ( FIG. 1 ) such that a rotation knob  52  rotates the frame  50  along with the end effector  14 . A distal end of the frame  50  has lateral recesses  54  that engage a proximal lip  56  of the staple channel  30 . The frame  50  includes a laterally centered, bottom firing slot  58  that passes longitudinally through the frame  50  for receiving a two-piece firing bar  60  comprised of a firing bar  62  with a distally attached E-beam  64 , the latter translating within the staple applying assembly  20  to sever and staple tissue. A distal portion of the frame  50  includes an upper cavity  66  whose distal and proximal ends communicate through distal and proximal apertures  68 ,  70 , defining there between a cross bar  72  over which a distally projecting clip  74  of a clip spring  76  engages with a lower spring arm  78 , distally and downwardly projecting through the upper cavity  66  to bias the firing bar  62  downwardly into engagement with the staple channel  30 , especially when the lower spring arm  78  encounters a raised portion  80  on the firing bar  62 . 
     Medical substance dispensing is integrated into the elongate shaft  18  by including a laterally offset cylindrical cavity  90  formed in the frame  50  that communicates along its longitudinal length to the outside via a rectangular aperture  92  that is slightly shorter than an electroactive polymer (EAP) syringe  100  that is inserted through the aperture  92  into the cylindrical cavity  90 . A proximal portion of the cylindrical cavity  90  contains a longitudinally aligned compression spring  102  that urges a distal dispensing cone  104  of the EAP syringe  100  distally into sealing contact with the frame  50  and allows translation for insertion and removal of the EAP syringe  100 . An electrical conductor  106  passes through the frame  50  and is attached to the compression spring  102 , which is also formed of an electrically conductive metal. An aft portion of the EAP syringe  100  is conductive and contacts the spring  102  to form a cathode to an EAP actuator  110  held in a proximal portion of the EAP syringe  100 . It will be appreciated that another conductor, perhaps traveling with the conductor  106 , also electrically communicates to the EAP actuator  110  to serve as the anode. 
     When activated, the EAP actuator  110  longitudinally expands, serving as a plunger to dispel a medical substance  112  in a distal portion of the EAP syringe  100  through the distal dispensing cone  104 . Insofar as the EAP actuator  110  laterally contracts to compensate for its longitudinal expansion, a plunger seal  114  maintains a transverse seal within the EAP syringe  100 . An vent (not shown), such as around conductor  106  allows air to refill the EAP syringe  100  behind the plunger seal  114  as the medical substance  112  is dispensed. The vent may rely upon the surface tension of the medical substance  112  to avoid leaking or be a one-way valve. As described below, the medical substance  112  is conducted by the frame  50  to a lateral fluid groove  120  that is formed in the firing bar  62  and the E-beam  64  to direct the medical substance to a cutting surface  122  of the E-beam  64 . The frame slot  58  is sized to seal the lateral fluid groove  120 . The portion of the lateral fluid groove  120  that is positioned under the spring clip  76  is sealed by a firing bar guide  124 . In the illustrative version, an outer sheath  130  encompasses the frame  50  and proximally projecting lever tray  40  of the anvil  12 . A top distal opening  131  allows closing of the anvil  12 . 
     An outer rectangular aperture  132  of the outer sheath  130  is sized and longitudinally positioned to correspond to the rectangular aperture  92  formed in frame  50 . In some applications, the outer sheath  130  may be rotated to selectively align the rectangular aperture  92  with the outer rectangular aperture  132  for insertion or removal of the EAP syringe  100 . It should be appreciated that in some applications that the EAP syringe  100  may be integrally assembled into an elongate shaft that does not allow for selecting a desired medical substance. For instance, a disposable implement portion with an integral staple cartridge and medical dispensing reservoir may be selected by the clinician as a unit. It is believed that allowing insertion at the time of use, though, has certain advantages including clinical flexibility in selecting a medical substance (e.g., anesthetics, adhesives, antibiotics, cauterizing compound, etc.) and extending the shelf life/simplifying storage and packaging of the implement portion  16 . 
     In the illustrative version, an elongate stack of many disk-shaped EAP layers are aligned longitudinally and configured to expand along this longitudinal axis. Electroactive polymers (EAPs) are a set of conductive doped polymers that change shape when electrical voltage is applied. In essence, the conductive polymer is paired to some form of ionic fluid or gel and electrodes. Flow of the ions from the fluid/gel into or out of the conductive polymer is induced by the voltage potential applied and this flow induces the shape change of the polymer. The voltage potential ranges from IV to 4 kV, depending on the polymer and ionic fluid used. Some of the EAPs contract when voltage is applied and some expand. The EAPs may be paired to mechanical means such as springs or flexible plates to change the effect that is caused when the voltage is applied. 
     There are two basic types of EAPs and multiple configurations of each type. The two basic types are a fiber bundle and a laminate version. The fiber bundle consists of fibers around 30-50 microns. These fibers may be woven into a bundle much like textiles and are often called EAP yarn because of this. This type of EAP contracts when voltage is applied. The electrodes are usually made up of a central wire core and a conductive outer sheath that also serves to contain the ionic fluid that surrounds the fiber bundles. An example of a commercially available fiber EAP material, manufactured by Santa Fe Science and Technology and sold as PANION™ fiber, is described in U.S. Pat. No. 6,667,825, which is hereby incorporated by reference in its entirety. 
     The other type is a laminate structure, which consists of a layer of EAP polymer, a layer of ionic gel and two flexible plates that are attached to either side of the laminate. When a voltage is applied, the square laminate plate expands in one direction and contracts in the perpendicular direction. An example of a commercially available laminate (plate) EAP material is from Artificial Muscle Inc, a division of SRI Laboratories. Plate EAP material is manufactured by EAMEX of Japan and is referred to as thin film EAP. 
     It should be noted that EAPs do not change volume when energized; they merely expand or contract in one direction while doing the opposite in the transverse direction. The laminate version may be used in its basic form by containing one side against a rigid structure and using the other much like a piston. The laminate version may also be adhered to either side of a flexible plate. When one side of the flexible plate EAP is energized, it expands flexing the plate in the opposite direction. This allows the plate to be flexed in either direction, depending on which side is energized. 
     An EAP actuator usually consists of numerous layers or fibers bundled together to work in cooperation. The mechanical configuration of the EAP determines the EAP actuator and its capabilities for motion. The EAP may be formed into long stands and wrapped around a single central electrode. A flexible exterior outer sleeve will form the other electrode for the actuator as well as contain the ionic fluid necessary for the function of the device. In this configuration when the electrical field is applied to the electrodes, the strands of EAP shorten. This configuration of EAP actuator is called a fiber EAP actuator. Likewise, the laminate configuration may be placed in numerous layers on either side of a flexible plate or merely in layers on itself to increase its capabilities. Typical fiber structures have an effective strain of 2-4% where the typical laminate version achieves 20-30%, utilizing much higher voltages. 
     For instance, a laminate EAP composite may be formed from a positive plate electrode layer attached to an EAP layer, which in turn is attached to an ionic cell layer, which in turn is attached to a negative plate electrode layer. A plurality of laminate EAP composites may be affixed in a stack by adhesive layers there between to form an EAP plate actuator. It should be appreciated that opposing EAP actuators may be formed that can selectively bend in either direction. 
     A contracting EAP fiber actuator may include a longitudinal platinum cathode wire that passes through an insulative polymer proximal end cap through an elongate cylindrical cavity formed within a plastic cylinder wall that is conductively doped to serve as a positive anode. A distal end of the platinum cathode wire is embedded into an insulative polymer distal end cap. A plurality of contracting polymer fibers are arranged parallel with and surrounding the cathode wire and have their ends embedded into respective end caps. The plastic cylinder wall is peripherally attached around respective end caps to enclose the cylindrical cavity to seal in ionic fluid or gel that fills the space between contracting polymer fibers and cathode wire. When a voltage is applied across the plastic cylinder wall (anode) and cathode wire, ionic fluid enters the contracting polymer fibers, causing their outer diameter to swell with a corresponding contraction in length, thereby drawing the end caps toward one another. 
     Returning to  FIG. 1 , the handle  22  controls closure of the anvil  12 , firing of the two-piece firing bar  60  ( FIG. 2 ), and dispensing of the medical substance. In an illustrative version, a pistol grip  140  may be grasped and a thumb button  142  depressed as desired to control closure of the anvil  12 . The thumb button  142  provides a proportional electrical signal to an EAP dispensing actuator not shown) similar to the EAP syringe  100  to transfer fluid through the conduits  46 ,  48  to the fluid bladders  24 ,  26  to close the anvil  12  ( FIG. 2 ). When the thumb button  142  is fully depressed, a mechanical toggle lock (not shown) engages to hold the thumb button  142  down until a full depression releases the toggle lock for releasing the thumb button  142 . Thus, when the thumb button  142  is held down, the surgeon has a visual indication that the end effector  14  is closed and clamped, which may be maintained in this position by continued activation of an EAP dispensing actuator or by a locking feature. For instance, control circuitry may sense movement of the thumb button  142 , causing a normally closed EAP shutoff valve (not shown) to open that communicates between the EAP dispensing actuator and the conduits  46 ,  48 . Once movement ceases, the EAP shutoff valve is allowed to close again, maintaining the anvil  12  position. In addition, a manual release could be incorporated to defeat such a lockout to open the anvil  12 . 
     As an alternative, a closure trigger (not shown) or other actuator may be included that bi-directionally transfers fluid to the fluid bladders  24 ,  26  as described in commonly owned U.S. patent application Ser. No. 11/061,908 entitled “SURGICAL INSTRUMENT INCORPORATING A FLUID TRANSFER CONTROLLED ARTICULATION MECHANISM” to Kenneth Wales and Chad Boudreaux, filed on Feb. 18, 2005, now U.S. Pat. No. 7,559,450, the disclosure of which is hereby incorporated by reference in its entirety. A number of such fluid actuators for articulation of a pivoting shaft are described that may be adapted for closing the anvil  12 . To take full advantage of the differential fluid transfer described for several of these versions, it should be appreciated that an opposing lift bag (not shown) may be placed above the lever tray  40  of the anvil  12  to assert an opening force as the left and right fluid bladders (lift bags)  24 ,  26  collapse. 
     With particular reference to  FIG. 3 , the handle  22  includes a firing trigger  150  ( FIG. 1 ) that is drawn proximally toward the pistol grip  140  to cause a firing rod  152  to move distally in a proximal portion  154  of the elongate shaft  18 . A distal bracket  156  of the firing rod  152  engages an upward proximal hook  158  of the firing bar  62 . A dynamic seal  160  within the frame  50  seals to the firing rod  152  so that the implement portion  16  is pneumatically sealed when inserted into an insufflated abdomen. 
     An anti-backup mechanism  170  of the firing rod  152  may be advantageously included for a handle  22  that includes a multiple stroke firing trigger  150  and a retraction biased firing mechanism coupled to the firing rod  152  (not shown). In particular, an anti-backup locking plate  172  has the firing rod  152  pass through a closely fitting through hole (not shown) that binds when a retracting firing rod  152  tips the lock plate  172  backward as shown with the bottom of the locking plate  172  held in position within the frame  50 . An anti-backup cam sleeve  174  is positioned distal to the anti-backup locking plate  172  and urged into contact by a more distal compression spring  176  through which the firing rod  152  passes and that is compressed within the frame  50 . It should be appreciated that mechanisms in the handle  22  may manually release the anti-backup mechanism  170  for retraction of the firing rod  152 . 
     In  FIGS. 4-5 , the end effector  14 , which in the illustrative version is a staple applying assembly  20 , is opened by having fluid bladder  24  deflated, drawing down lever tray  40  of the anvil  12 , which pivots about pin  32  raising distal clamping section  41  thereby allowing positioning body tissue  180  between the anvil  12  and staple cartridge  42 . The E-beam  64  has an upper pin  182  that resides within an anvil pocket  184  allowing repeated opening and closing of the anvil  12 . An anvil slot  186  formed along the length of the anvil  12  receives the upper pin  182  when the anvil  12  is closed and the two piece firing bar  60  is distally advanced. A middle pin  188  slides within the staple cartridge  42  above the staple channel  30  in opposition to a bottom pin or foot  190  that slides along a bottom surface of the staple channel  30 . 
     In  FIGS. 6-7 , the staple applying assembly  20  has been closed by expanding the fluid bladder (lift bag)  24 , raising the lever tray  40  of the anvil  12  until flush with the outer sheath  130 , with a proximal upwardly bent tip  192  of the lever tray  40  allowed to enter the top distal opening  131 . This bent tip  192  in combination with the opening  131 , advantageously allows greater radial travel for the anvil  12  as well as presenting an abutting surface rather than a piercing tip to the underlying fluid bladder  24 . When the anvil  12  is closed, the upper pin  182  is aligned with the anvil slot  186  for firing and the tissue  180  is flattened to a thickness appropriate for severing and stapling. 
     In  FIGS. 7-8 , the E-beam  64  is cut away to show its bottom foot  190  riding along a downwardly open laterally widened recess  200  that communicates with a narrow longitudinal slot  202  through which a vertical portion  204  of the E-beam  64  passes. A proximal aperture  206  to the narrow longitudinal slot  202  allows an assembly entrance for the lower foot  190 . A bottom bump  208  is positioned on the firing bar  62  to drop into the proximal aperture  206  during an initial portion of firing travel under the urging of the clip spring  76  ( FIG. 6 ) against the raised portion  80  of the firing bar  62  for proper engagement and for possible interaction with an end effector firing lockout mechanism (not shown). Also, this position allows for the end effector  14  to be pinched shut to facilitate insertion through a surgical entry point such as a cannula of a trocar (not shown). With reference to  FIGS. 8-10 , the firing bar guide  124  laterally contacts a portion of the firing bar  62  to close the corresponding portion of the lateral fluid groove  120 . In  FIG. 11 , the EAP syringe  100  in the cylindrical cavity  90  has its distal dispensing cone  104  communicating with a radial fluid passage  220  formed in the frame  50  that communicates in turn with the lateral fluid groove  120 . In  FIG. 12 , before installation in the surgical stapling and severing instrument  10 , the EAP syringe  100  may be advantageously sealed with a disposable cap  230 . In  FIGS. 13-14 , the EAP syringe  100  is shown without the disposable cap  230  and urged by spring  102  distally to engage the distal dispensing cone  104  into communication with the radial fluid passage  220 . 
     It should be appreciated that one or more sensor in the surgical stapling and severing instrument  10  may sense a firing condition (e.g., movement of firing bar or mechanism coupled to the firing bar, position of the firing trigger, a separate user control to dispense, etc.) and activate dispensing control circuitry to effect dispensing. 
     In  FIGS. 15-18 , an alternate two-piece firing bar  300  is formed from longitudinally laminated left half and right half firing bar portions  302 ,  304  that form a firing bar  305  and attached to an E-beam  309 . Thereby, fluid transfer down the firing bar  300  may be further constrained. In particular, a left side fluid groove  310  in the left half firing bar portion  302  transitions distally to a pair of aligned internal fluid grooves  312 ,  314  respectively in the left and right half firing bar portions  302 ,  304 , defining an internal fluid passage  316 . Since the E-beam  309  is laterally thicker and of short longitudinal length, a drilled fluid passage  320  is formed therein between a cutting surface  322  and an aft edge aligned to communicate with the internal fluid passage  316 . 
     While the present embodiment has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art. 
     For example, while a non-articulating shaft is described herein for clarity, it should be appreciated that medical substance dispensing may be incorporated into an articulating shaft. In addition, fluid conduits may be incorporated that pass through an articulation joint of a shaft to fluid bladder actuators that close an end effector. 
     As another example, while both medical substance dispensing and fluid actuated anvil closing are illustrated herein, applications consistent with aspects of various embodiments may include either of these features. Further, for applications in which an adhesive and/or cauterizing medical substance is dispensed, it should be appreciated that features such as staples may be omitted. 
     As another example, while a staple applying assembly  20  is illustrated herein, it should be appreciated that other end effectors (graspers, cutting devices, etc.) may benefit from either or both of fluid controlled closing and medical substance dispensing. 
     As yet another example, a receptacle for the EAP syringe may be formed in the handle rather than in the elongate shaft. 
     As yet an additional example, a symmetric arrangement for a second EAP syringe may be formed in the elongate channel so that two medical substances may be simultaneously dispensed during firing. 
     As yet a further example, while a staple applying apparatus provides an illustrative embodiment, it should be appreciated that other endoscopic instruments may benefit from the ability to dispense a liquid at or near a distal end thereof. Examples of instruments that may benefit include, but are not limited to, an ablation device, a grasper, a cauterizing tool, an anastomotic ring introduction device, a surgical stapler, a linear stapler, etc. As such, those instruments that do not employ a firing bar that serves herein as a convenient fluid passage to a cutting surface may instead incorporate ducting or fluid conduits to an appropriate location. 
     While an electroactive polymer plunger has various advantages, it should be appreciated that other types of actuated devices may be employed to dispense a medical substance to the end effector. 
     For example,  FIGS. 19-20  illustrate various embodiments of a disposable loading unit  1010 , with  FIG. 20  showing an exploded view of the disposable loading unit  1010 . The disposable loading unit  1010  includes a first end  1012  configured for releasable connection to a surgical instrument (see  FIG. 33 ), and a second end  1014  opposite the first end  1012 . The disposable loading unit  1010  comprises a housing assembly  1016 , an agent cartridge  1018 , a knife assembly  1020 , a staple cartridge  1022 , and an anvil assembly  1024 . The disposable loading unit  1010  may be removed and discarded after a single use. 
     The housing assembly  1016  comprises a channel  1026  and a channel cover  1028  connected to the channel  1026 . The channel  1026  and the channel cover  1028  may be fabricated from any suitable material such as, for example, a plastic. The channel  1026  includes a first end  1030  proximate the first end  1012  of the disposable loading unit  1010  and a second end  1032  proximate the second end  1014  of the disposable loading unit  1010 . The channel  1026  comprises a base  1034 , a first wall  1036 , and a second wall  1038 . According to various embodiments, the base  1034  defines an opening  1040  proximate the first end  1030  of the channel  1026 , a first slot  1042  proximate the first end  1030  of the channel  1026 , a second slot  1044  proximate the first end  1030  of the channel  1026 , and a third slot  1046  proximate the second end  1032  of the channel. The first wall  1036  is connected to the base  1034  and extends generally perpendicular therefrom. The second wall  1038  is connected to the base  1034 , extends generally perpendicular therefrom, and is opposite the first wall  1036 . The second wall  1038  may be a mirror-image of the first wall  1036 , and the first and second walls  1036 ,  1038  may be fabricated integral with the base  1034 . According to various embodiments, each of the first and second walls  1036 ,  1038  define a fourth slot  1048 , a first tab  1050 , a first indent  1052 , a fifth slot  1054 , a second indent  1056 , a sixth slot  1058 , a third indent  1060 , a fourth indent  1062 , a seventh slot  1064 , an eighth slot  1066 , and a first flange  1068 . 
     The channel cover  1028  includes a first end  1070  proximate the first end  1012  of the disposable loading unit  1010  and a second end  1072  opposite the first end  1070 , and may be symmetric along an axis that extends from the first end  1070  of the channel cover  1028  to the second end  1072  of the channel cover  1028 . The channel cover  1028  is configured to engage with the channel  1026  at a plurality of locations. According to various embodiments, the channel cover  1028  defines a pair of coupling pegs  1074  proximate the first end  1070  of the channel cover  1028  that extends from the channel cover  1028 . One of the coupling pegs  1074  passes through the opening  1040  defined by the channel  1026 . The channel cover  1028  also defines a slit  1076  proximate the second end  1072  of the channel cover  1028 . According to various embodiments, the channel cover  1028  defines a first pair of tabs  1078  that pass through and engage with the fourth slots  1048 , a first pair of interior projections that mate with the first indents  1052 , a second pair of tabs  1080  that pass through and engage with the fifth slots  1054 , a second pair of interior projections that mate with the second indents  1056 , and a third pair of interior projections that engage with the sixth slots  1058 . According to other embodiments, the channel  1026  and the channel cover  1028  may be fabricated to include other arrangements of tabs, slots, projections, indents, etc. that may be utilized to connect the channel cover  1028  to the channel  1026 . 
     The agent cartridge  1018  is connected to the housing assembly  1016  and houses at least one medical agent. The medical agent may be any type of medical agent. For example, the medical agent may comprise an anesthetic, an adhesive, an antibiotic, a cauterizing substance, a coagulant, a growth hormone, a hemostatic agent, a sealant, etc., or any combination thereof. 
     The agent cartridge  1018  includes a first end  1082  proximate the first end  1012  of the disposable loading unit  1010  and a second end  1084  opposite the first end  1082 . The agent cartridge  1018  comprises a body  1086  (see  FIG. 24 ) that may be fabricated from any suitable material (e.g., a plastic) that is compatible with the medical agent. According to various embodiments, the body  1086  comprises a first section  1088  and a second section  1090 . The first section  1088  may define a first spline that extends therefrom, and passes through and engages with the first slot  1042  of the base  1034  of the channel  1026 . As shown in  FIG. 21 , the first section  1088  may also define a first projection  1094  and a first dispensing port  1096  proximate the second end  1084  of the agent cartridge  1018 . The first projection  1094  may be of any shape (e.g., rectangular, triangular, hemispherical, etc.). The first dispensing port  1096  is positioned between the first projection  1094  and the second end  1084  of the agent cartridge  1018 . The second section  1090  is spaced apart from the first section  1088  and may be a mirror-image thereof. The second section  1090  may define a second spline that extends therefrom, and passes through and engages with the second slot  1044  of the base  1034  of the channel  1026 . As shown in  FIG. 21 , the second section  1090  may define a second projection  1100  and a second dispensing port  1102  proximate the second end  1084  of the agent cartridge  1018 . The second projection  1100  may be of any shape (e.g., rectangular, triangular, hemispherical, etc.). The second dispensing port  1102  is positioned between the second projection  1100  and the second end  1084  of the agent cartridge  1018 . According to other embodiments, the body  1086  may be fabricated to include other arrangements of splines, tabs, fasteners, etc. that may be utilized to connect the agent cartridge  1018  to the housing assembly  1016 . 
     According to various embodiments, the agent cartridge  1018  also comprises a first sealing member  1104  (see  FIG. 21 ) and a second sealing member  1106  (see  FIG. 21 ). The first sealing member  1104  is connected to the first section  1088  and cooperates with the first section  1088  to house a medical agent. Similarly, the second sealing member  1106  is connected to the second section  1090  and cooperates with the second section  1090  to house a second medical agent. The first medical agent may be the same or different than the second medical agent. 
     The knife assembly  1020  is connected to the housing assembly  1016 , and includes a first end  1108  proximate the first end  1012  of the disposable loading unit  1010  and a second end  1110  opposite the first end  1108 . The knife assembly  1020  comprises a body  1112  and a cutting surface  1114 . According to various embodiments, the cutting surface  1114  comprises a portion of a knife blade that is connected to the body  1112  proximate the second end  1110  of the knife assembly  1020 . The body  1112  may be fabricated from any suitable material such as, for example, a plastic. According to various embodiments, the body  1112  comprises a first clamping member  1116  proximate the first end  1108  of the knife assembly  1020 , a second clamping member  1118  proximate the first end  1108  of the knife assembly  1020 , and a foot member  1120  proximate the second end  1110  of the knife assembly  1020 . The foot member  1120  passes through the third slot  1046  of the base  1034  of the channel  1026  and is mated with a retainer  1122  that is external to the housing assembly  1016  and serves to slidably connect the body  1112  to the housing assembly  1016  such that the knife assembly  1020  can be selectively advanced along the third slot  1046  toward the second end  1032  of the channel  1026 . 
     The body  1112  of the knife assembly  1020  also comprises a first surface  1124  and a second surface  1126  (see  FIG. 24 ) that is opposite the first surface  1124 . The first surface  1124  of the body  1112  is adjacent the first section  1088  of the agent cartridge  1018 , and the second surface  1126  of the body  1112  is adjacent the second section  1090  of the agent cartridge  1018 . The first surface  1124  of the body  1112  defines a first groove  1128  and the second surface  1126  of the body  1112  defines a second groove  1130  (see  FIG. 24 ). The first groove  1128  is proximate the cutting surface  1114  of the knife assembly  1020  and may extend any distance along the first surface  1124  of the body  1112  toward the first end  1108  of the knife assembly  1020 . The first groove  1128  is adjacent the first dispensing port  1096  and is configured to receive the first projection  1094  of the first section  1088  of the body  1086 . The second groove  1130  is proximate the cutting surface  1114  of the knife assembly  1020  and may extend any distance along the second surface  1126  of the body  1112  toward the first end  1108  of the knife assembly  1020 . The second groove  1130  is adjacent the second dispensing port  1102  and is configured to receive the second projection  1100  of the second section  1090  of the body  1086 . Each of the first and second grooves  1128 ,  1130  may be of any shape (e.g., rectangular, triangular, hemispherical, etc.) suitable for respectively receiving the first projection  1094  and the second projection  1100 . The body  1112  of the knife assembly  1020  may also define an opening  1132  that extends from the first surface  1124  to the second surface  1126  proximate the second end  1110  of the knife assembly  1020 . 
     The staple cartridge  1022  is connected to the housing assembly  1016 . The staple cartridge  1022  includes a first end  1134  and a second end  1136  opposite the first end  1134 . The second end  1136  of the staple cartridge  1022  is proximate the second end  1014  of the disposable loading unit  1010 . The staple cartridge  1022  may be similar to other staple cartridges known in the art. For example, the staple cartridge  1022  may comprise a plurality of surgical fasteners and a plurality of corresponding pushers. According to various embodiments, the staple cartridge  1022  defines a slot  1142  that is aligned with the third slot  1046  of the base  1034  of the channel  1026  and extends from the first end  1134  of the staple cartridge  1022  toward the second end  1136  of the staple cartridge  1022 . The staple cartridge  1022  may also define tabs that extend from the staple cartridge  1022  and pass through and engage with the seventh slots  1064  and the eighth slots  1066  of the channel  1026 , and may further comprise flanges  1146  which frictionally engage the first and second walls  1036 ,  1038  of the channel  1026  proximate the second end  1032  of the channel  1026 . According to other embodiments, the staple cartridge  1022  may be fabricated to include other arrangements of tabs, flanges, fasteners, etc. that may be utilized to connect the staple cartridge  1022  to the housing assembly  1016 . 
     The anvil assembly  1024  is connected to the housing assembly  1016 . The anvil assembly  1024  includes a first end  1148  and a second end  1150  opposite the first end  1148 . The second end  1150  of the anvil assembly  1024  is proximate the second end  1014  of the disposable loading unit  1010 . The anvil assembly  1024  may be similar to other anvil assemblies known in the art. For example, the anvil assembly  1024  is moveable between an open position and a closed position, and may comprise an anvil plate  1152  and an anvil body  1154  connected to the anvil plate  1152 . According to various embodiments, the anvil plate  1152  defines a slot  1156  that is aligned with the slot  1142  of the staple cartridge  1022 , and the anvil body  1154  defines a slot  1158  that is aligned with the slot  1156  of the anvil plate  1152 . The anvil plate  1152  may also define a first pair of ears  1160  proximate the first end  1148  of the anvil assembly  1024  and a second pair of ears  1162  positioned between the first pair of ears  1160  and the second end  1150  of the anvil assembly  1024 . One of the ears of the second pair of ears  1162  is engaged with the third indent  1060  defined by the first wall  1036  of the channel  1026 , and the other ear of the second pair of ears  1162  is engaged with the third indent  1060  defined by the second wall  1038  of the channel  1026 . A spring member  1164  or other biasing arrangement may be utilized to urge the anvil assembly  1024  to the open position, and an anvil pin  1166  that passes through the opening  1132  of the knife assembly  1020  may be utilized to urge the anvil assembly  1024  toward the closed position. According to other embodiments, the anvil assembly  1024  may be fabricated to include other fastener arrangements that may be utilized to connect the anvil assembly  1024  to the housing assembly  1016 . 
     The disposable loading unit  1010  may further comprise a first medical agent driver  1168  proximate the first end  1082  of the agent cartridge  1018  and a second medical agent driver  1170  (see  FIG. 24 ) proximate the first end  1082  of the agent cartridge  1018 . According to various embodiments, the first and second medical agent drivers  1168 ,  1170  may comprise a portion of a drive block  1172  that is coupled to the knife assembly  1020  at the first end  1108  thereof. For such embodiments, the first medical agent driver  1168  may be configured to slidably fit within the first section  1088  of the body  1086  of the agent cartridge  1018 , and the second medical agent driver  1170  may be configured to slidably fit within the second section  1090  of the body  1086  of the agent cartridge  1018 . According to other embodiments, the first medical agent driver  1168  may comprise an electrically activated polymer that is in contact with the first section  1088  of the body  1086  of the agent cartridge  1018  as shown in  FIGS. 13 and 14 . Similarly, the second medical agent driver  1170  may comprise an electrically activated polymer that is in contact with the second section  1090  of the body  1086  of the agent cartridge  1018 . For such embodiments, each of the first and second medical agent drivers  1168 ,  1170  may be electrically connected to a contact  1174  (see  FIG. 32 ) that is proximate the first end  1012  of the disposable loading unit  1010  and is connected to a voltage source. 
     As shown in  FIG. 2 , the disposable loading unit  1010  may also comprise a lock member  1176  connected to the drive block  1172 , a retainer  1178  for coupling the lock member  1176  to the drive block  1172 , and a sled  1180  positioned proximate the second end  1110  of the knife assembly  1020 . The drive block  1172 , the lock member  1176 , the retainer  1178  and the sled  1180  may be similar to those known in the art. The disposable loading unit  1010  may further comprise a firing member adapter  1182  connected to the drive block  172 . The firing member adapter  1182  is configured for receiving a firing member that does not comprise a portion of the disposable loading unit  1010 . 
       FIG. 22  illustrates various embodiments of the disposable loading unit  1010 . For purposes of clarity only, certain portions of the disposable loading unit  1010  are not shown in this figure. The first and second clamping members  1116 ,  1118  are connected to the drive block  1172 , and the lock member  1176  and the retainer  1178  are also connected to the drive block  1172 . The first medical agent driver  1168  is connected to the drive block  1172 , and the sled  1180  is proximate the second end  1110  of the knife assembly  1020 . The general positions of the shown components relative to the channel  1026  represent the positions of the components prior to the advancement of the firing member (i.e., the pre-fire positions). 
       FIG. 23  illustrates various embodiments of the disposable loading unit  1010 . For purposes of clarity only, certain portions of the disposable loading unit  1010  are not shown in this figure.  FIG. 23  is similar to  FIG. 22 , and shows that the first medical agent driver  1168  is aligned with the first section  1088  of the body  1086  of the agent cartridge  1018 . The general positions of the shown components relative to the channel  1026  represent the positions of the components prior to the advancement of the firing member (i.e., the pre-fire positions). 
       FIG. 24  illustrates various embodiments of the disposable loading unit  1010 , and shows a cross-section of the disposable loading unit  1010  along line  6 - 6  of  FIG. 23 . As shown in  FIG. 24 , the first and second dispensing ports  1096 ,  1102  may pass through the respective first and second sections  1088 ,  1090  at an angle relative to the base  1034  of the channel  1026 . 
       FIG. 25  illustrates various embodiments of the disposable loading unit  1010 . For purposes of clarity only, certain portions of the disposable loading unit  1010  are not shown in this figure. The anvil assembly  1024  is shown in the open position relative to the staple cartridge  1022  in  FIG. 25 . The general positions of the shown components relative to the channel  1026  represent the positions of the components prior to the advancement of the firing member (i.e., the pre-fire positions). 
       FIG. 26  illustrates various embodiments of the disposable loading unit  1010 . For purposes of clarity only, certain portions of the disposable loading unit  1010  are not shown in this figure.  FIG. 26  is similar to  FIG. 25 , but also shows the first section  1088  of the body  1086  of the agent cartridge  1018 . 
       FIG. 27  illustrates various embodiments of the disposable loading unit  1010 , and is an enlarged version of a portion of the disposable loading unit  1010  illustrated in  FIG. 26 . 
       FIG. 28  illustrates various embodiments of the disposable loading unit  1010 , and is an enlarged version of a portion of the disposable loading unit  1010  illustrated in  FIG. 26 . 
       FIG. 29  illustrates various embodiments of the disposable loading unit  1010 . For purposes of clarity only, certain portions of the disposable loading unit  1010  are not shown in this figure. The general positions of the shown components relative to the channel  1026  represent the positions of the components after the advancement of the firing member (i.e., the post-fire positions). As shown in  FIG. 29 , the anvil assembly  1024  is in the closed position, and the post-fire positions of the knife assembly  1020 , the anvil assembly  1024 , the first medical agent driver  1168 , the drive block  1172 , and the lock member  1176  are different than their pre-fire positions relative to the channel  1026 . 
       FIG. 30  illustrates various embodiments of the disposable loading unit  1010 , and is an enlarged version of a portion of the disposable loading unit  1010  illustrated in  FIG. 29 . As shown in  FIG. 30 , the post-fire position of the first medical agent driver  1168  may be some distance from the first dispensing port  1096 . Similarly, the post-fire position of the second medical agent driver  1170  may be some distance from the second dispensing port  1102 . 
       FIG. 31  illustrates various embodiments of the disposable loading unit  1010 . For purposes of clarity only, certain portions of the disposable loading unit  1010  are not shown in this figure.  FIG. 31  is similar to  FIG. 22 , but shows the first section  1088  of the body  1086  of the agent cartridge  1018 , and also shows the first medical agent driver  1168  embodied as an electrically activated polymer.  FIG. 31  also illustrates the conductors  1184  that electrically connect the first medical agent driver  1168  and the contact  1174 . The general positions of the shown components relative to the channel  1026  represent the positions of the components prior to the advancement of the firing member (i.e., the pre-fire positions). 
       FIG. 32  illustrates various embodiments of the disposable loading unit  1010 . For purposes of clarity only, certain portions of the disposable loading unit  1010  are not shown in this figure.  FIG. 32  is similar to  FIG. 26 , but shows the first medical agent driver  1168  embodied as an electrically activated polymer.  FIG. 32  also illustrates the contact  1174  and the conductors  1184  that electrically connect the contact  1174  and the first medical agent driver  1168 . The general positions of the shown components relative to the channel  1026  represent the positions of the components prior to the advancement of the firing member (i.e., the pre-fire positions). 
       FIG. 33  illustrates various embodiments of a surgical instrument  1200 . The surgical instrument  1200  includes a handle assembly  1202 , an elongated body  1204  connected to the handle assembly  1202 , and a disposable loading unit  1010  releasably connected to the elongated body  1204 . The disposable loading unit  1010  may be releasably connected to the elongated body  1204  in any manner. For example, the disposable loading unit  1010  may be releasably connected to the elongated body  1204  via the coupling pegs  1074  described hereinabove. The handle assembly  1202  and the elongated body  1204  may be similar to other handle assemblies and elongated bodies known in the art. For example, the handle assembly  1202  may include means for advancing a firing member that is surrounded by the elongated body  1204  and is utilized to advance the drive block  1172  of the disposable loading unit  1010 . 
     In operation, when the firing member is advanced, the advancement of the firing member causes the drive block  1172  to advance toward the second end  1014  of the disposable loading unit  1010 . As the drive block  1172  advances, the knife assembly  1020  advances toward the second end  1014  of the disposable loading unit  1010 . The advancement of the knife assembly  1020  causes the anvil pin  1166  to cooperate with the anvil body  1154  to urge the anvil assembly  1024  toward the closed position. The advancement of the knife assembly  1020  also causes the sled  1180  to advance toward the second end  1014  of the disposable loading unit  1010 . As the sled  1180  advances, the angled leading edges of the sled  1180  sequentially contact pushers supported within the staple cartridge  1022 , causing the pushers to urge surgical fasteners from the staple cartridge  1022  in a known manner. 
     For embodiments where the first and second medical agent drivers  1168 ,  1170  are coupled to the knife assembly  1020 , the advancement of the drive block  1172  advances the first and second medical agent drivers  1168 ,  1170  within the first and second sections  1088 ,  1090  of the body  1086  toward the second end  1084  of the agent cartridge  1018 . As the first and second medical agent drivers  1168 ,  1170  advance, they make contact with the first and second sealing members  1104 ,  1106  and urge the first and second medical agents out of the first and second dispensing ports  1096 ,  1102 . Because the post-fire positions of the first and second medical agent drivers  1168 ,  1170  may be some distance from the first and second dispensing ports  1096 ,  1102 , some medical agent may still remain housed by the agent cartridge  1018  after the first and second medical agent drivers  1168 ,  1170  advance from their pre-fire positions to their post-fire positions. 
     For embodiments where the first and second medical agent drivers  1168 ,  1170  are electrically activated polymers, the advancement of the firing member causes an electrical connection to be made with the contact  1174 , causing a voltage to be applied to the first and second medical agent drivers  1168 ,  1170 . In response to the applied voltage, the first and second medical agent drivers  1168 ,  1170  expand within the first and second sections  1088 ,  1090  of the body  1086  of the agent cartridge  1018  and urge the first and second medical agents out of the first and second dispensing ports  1096 ,  1102 . 
     With the first projection  1094  and the second projection  1100  serving as stops which restrict the flow of the first and second medical agents along the grooves  1128 ,  1130  in the direction toward the first end  1012  of the disposable loading unit  1010 , the medical agents urged out of the first and second dispensing ports  1096 ,  1102  advance along the respective grooves  1128 ,  1130  toward the cutting surface  1114  of the disposable loading unit  1010 . As the knife assembly  1020  advances along the slot  1142  defined by the staple cartridge  1022 , the staple cartridge  1022  also serves to keep the medical agents in the grooves  1128 ,  1130  until the medical agents exit the grooves  1128 ,  1130  proximate the cutting surface  1114 . The medical agents are thus effectively delivered to the site of the cutting and stapling. 
     After a single use, the disposable loading unit  1010  is removed from the elongated body  1204  and may be replaced with another disposable loading unit  1010  for another use. This process may be repeated any number of times. Therefore, the handle assembly  1202  and the elongated body  1204  connected thereto may be reused any number of times. 
     While several embodiments have been described, it should be apparent, however, that various modifications, alterations and adaptations to those embodiments may occur to persons skilled in the art with the attainment of some or all of the advantages of the various embodiments. For example, according to various embodiments, a single component may be replaced by multiple components, and multiple components may be replaced by a single component, to perform a given function or functions. This application is therefore intended to cover all such modifications, alterations and adaptations without departing from the scope and spirit of the disclosed embodiments as defined by the appended claims. 
     Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.