An injection device which includes a housing (12), a needle hub (38) slidable within the housing (12), a needle (40) having a distal end piercing tip (42) and a proximal end piercing tip (44), the needle hub (40) being moveable from a first position wherein the distal piercing tip (42) is within the housing to a second position wherein the distal end piercing tip (42) extends outwardly of housing (12), a first spring (23) biasing the needle hub (38) towards the first position, and a cartridge receiving member (48) mounted within the housing, and a plunger rod assembly (166), the plunger rod assembly (166) having a distal interior chamber (102) and a proximal interior chamber (103), the distal interior chamber (102) being designed to receive a cartridge (85) containing a liquid (89), the cartridge having a septum (87) and a plunger (88) to prevent exit of the liquid, and a second needle hub (91) located in the proximal chamber, a second hollow needle (92) mounted in the second needle hub, the second hollow needle having a distal piercing tip (94) and a proximal piercing tip (93), the second hollow needle being moveable from a first non piercing position to a second position whereby said distal piercing tip (94) will pierce the septum (87).L'invention concerne un dispositif d'injection qui comprend un logement (12), un connecteur d'aiguille (38) pouvant coulisser au sein du logement (12), une aiguille (40) ayant une pointe de perçage (42) d'extrémité distale et une pointe de perçage (44) d'extrémité proximale, le connecteur d'aiguille (40) étant mobile d'une première position à laquelle la pointe de perçage distale (42) se trouve au sein du logement à une seconde position à laquelle la pointe de perçage (42) d'extrémité distale s'étend vers l'extérieur du logement (12), un premier ressort (23) sollicitant le connecteur d'aiguille (38) en direction de la première position, et un élément de réception (48) de cartouche monté dans le logement, et un ensemble de tige de pi
