referring to the drawings in greater detail and by reference characters thereto , there is illustrated a mixing and transfer assembly generally designated by reference numeral 10 . transfer and mixing assembly 10 includes a by - pass cartridge generally designated by reference numeral 12 , an outer housing about by - pass cartridge 12 and generally designated by reference numeral 14 , an activation cap 16 , a plunger rod 18 , a syringe 20 and a syringe plunger rod 22 . by - pass cartridge 12 has an outer wall 26 with a by - pass 28 formed therein as is known in the art . a septum 30 covers the outlet of by - pass cartridge 12 and a cap 32 extends thereover . mounted within by - pass cartridge 12 is a rear plunger 34 which has a female luer fitting 36 . an intermediate or middle plunger 38 is situated rearwardly of by - pass 28 . there is thus formed a rear compartment 40 which is defined as the space between wall 26 , rear plunger 34 and intermediate plunger 38 . a front compartment 42 is defined by wall 26 , intermediate plunger 38 and septum 30 . for most uses , rear compartment 40 will contain the diluent while a front compartment 42 will contain the dry and active pharmaceutical component . plunger rod 18 includes a head 46 for ease in pushing on shaft 48 . shaft 48 is provided with a male luer fitting 50 designed to engage with luer fitting 36 on rear plunger 34 . outer housing 54 surrounds and supports by - pass cartridge 12 and includes a side wall 54 and a top wall 56 . a piercing member 58 has a bore 60 extending therethrough while an upper luer female fitting 62 is provided . syringe 20 includes a conventional syringe body 66 having a flange 68 at the end thereof . syringe body 66 is provided with a luer fitting 70 designed to engage luer fitting 62 in outer housing 14 . mounted interiorly of syringe body 66 is a plunger 72 which has a passageway 74 extending therethrough . a hydrophobic membrane 76 covers passageway 74 . syringe plunger rod 22 includes a shaft 80 having a head 82 at one end thereof and a base 84 . in operation , activation cap 16 is used to push by - pass cartridge 12 forwardly such that septum 30 is pierced thereby and a fluid passageway between syringe 20 and front compartment 42 is established . subsequently , plunger rod 18 is attached to rear plunger 34 and pressure exerted thereon . the liquid in rear compartment 40 is substantially incompressible and accordingly , pressure is exerted on intermediate plunger 38 to move it forwardly to the area of by - pass 28 . at this point , the diluent can enter into front compartment 42 to mix with the pharmaceutical component therein . a continued advancement by pressure on plunger rod 18 will cause both plungers 34 , 38 to advance and air contained within front compartment 42 will pass through bore 60 of piercing member 58 . the air will enter syringe body 66 and be expelled through passageway 74 . in the meantime , hydrophobic membrane 76 will prevent passage of any liquid therethrough . the continued advancement of plungers 34 , 38 will force the mixture into syringe body 66 with plunger 72 being forced rearwardly . once all the mixture has been moved to syringe body 66 , plunger rod 22 may then be activated to cause the mixture to move into front compartment 42 . this back and forth movement may be continued as long as needed to ensure the proper mixing of the components . the passing through bore 60 which is relatively small will ensure the mixing of the two components while preventing any foaming or air bubbles . preferably , plunger rod 22 is not secured to plunger 72 . this will prevent any aspiration movement which would permit air to enter the mixture . as shown in fig3 a , 3 b and 3 c , plunger 72 may take several different forms . thus , plunger 72 may have an insert 90 about which resilient material 92 extends . hydrophobic membrane 94 extends across the top thereof . in the embodiment of fig2 b , hydrophobic membrane 94 merely extends across resilient material 92 . in the embodiment of fig2 c , hydrophobic membrane 94 is sandwiched between two portions of resilient material 92 . turning to the embodiment of fig4 , there is illustrated a mixing and transferring device similar to that illustrated in fig1 and similar reference numerals in the 100 &# 39 ; s are employed for similar components . in this embodiment , plunger rod 118 has a shaft 148 with threads 115 formed on a portion thereof . threads 115 engage with flange 127 formed on activation cap 116 . this arrangement permits a relatively slow movement of the plungers as the initial movement is dependent on the turning of plunger rod 118 . after threads 115 have finished , a final pushing motion may be employed as in the previously described embodiment . in the embodiment of fig5 , reference numerals in the 200 &# 39 ; s are utilized for similar components . transfer and mixing device 210 includes a plunger rod 248 which has a plurality of teeth 229 formed on one side thereof . a housing 231 is secured to activation cap 216 . housing 231 includes a rotatable pinion 233 by means of a thumb wheel 235 . thus , movement of thumb wheel 235 will drive plunger rod 218 in a manner previously described . a cap 237 is mounted about plunger rod 218 and may be removed for a final pushing action thereon . also , as will be noted in this drawing , syringe 220 has a coil spring 239 mounted therein . a cap 241 is used for covering the end of syringe body 266 . with the arrangement of fig5 , transfer of the mixture into syringe 220 will continue as long as pressure is exerted on plunger rod 218 . once pressure has been removed , spring 239 will bias plunger 272 and the mixture will automatically be returned to front compartment 242 . in fig6 , reference numerals in the 300 &# 39 ; s are employed with similar reference numerals designating similar components . the plunger rod 318 , in this embodiment , includes a plurality of teeth 343 on the end of shaft 348 proximate head 346 . in this arrangement , cap 337 must be removed and plunger rod 318 rotated such that teeth 343 will then engage pinion 333 . in fig7 , there is illustrated a front cap which could be employed with the outer housing of the previous embodiments . cap 351 includes a hydrophobic membrane 353 extending over an internal passageway with a male luer connection 355 . it will be understood that the above described embodiments are for purposes of illustration only and that changes and modifications may be made thereto without departing from the spirit and scope of the invention .