A mixing syringe comprising: a first chamber adapted for containing an injectable material; a second chamber in axial alignment with said first chamber and adapted for containing an injectable material; a cannula having an end open to said first chamber, a projection spaced apart from the open end thereof, and a lateral opening spaced apart from the open end and projection thereof; a mixing assembly comprising an elongated sealing element disposed between said first and said second chambers (60, 74), said elongated sealing element having an internal passage for slidably receiving said cannula and supporting said cannula for axial movement; said elongated sealing element being at least partially disposed within said first chamber and said second chamber and completely covering said lateral opening of said cannula when said cannula is in an inoperative position; said projection being spaced apart from said elongated sealing element when said cannula is in an inoperative position; and a retracting element attached to said cannula, said retracting element comprising means for creating axial movement of said cannula such that said cannula is retracted from said inoperative position to an operative position; wherein as said cannula is retracted from said inoperative position to said operative position, said lateral opening moves from said internal passage of said elongating sealing element into said second chamber so that said second chamber is in fluid communication with said first chamber, and said projection moves to abut a distal end of said elongated sealing element causing said elongated sealing element to move into said second chamber expelling substantially all the injectable material contained in said second chamber through said cannula and into said first chamber; and wherein said cannula does not puncture a seal, no air is introduced into either the first chamber or the second chamber, and a combined volume of the first chamber and second chamber remains constant when moving said cannula from said inoperative position to said operative position. a first chamber adapted for containing an injectable material; a second chamber in axial alignment with said first chamber and adapted for containing an injectable material; a cannula having an end open to said first chamber, a projection spaced apart from the open end thereof, and a lateral opening spaced apart from the open end and projection thereof; a mixing assembly comprising an elongated sealing element disposed between said first and said second chambers (60, 74), said elongated sealing element having an internal passage for slidably receiving said cannula and supporting said cannula for axial movement; said elongated sealing element being at least partially disposed within said first chamber and said second chamber and completely covering said lateral opening of said cannula when said cannula is in an inoperative position; said projection being spaced apart from said elongated sealing element when said cannula is in an inoperative position; and a retracting element attached to said cannula, said retracting element comprising means for creating axial movement of said cannula such that said cannula is retracted from said inoperative position to an operative position; wherein as said cannula is retracted from said inoperative position to said operative position, said lateral opening moves from said internal passage of said elongating sealing element into said second chamber so that said second chamber is in fluid communication with said first chamber, and said projection moves to abut a distal end of said elongated sealing element causing said elongated sealing element to move into said second chamber expelling substantially all the injectable material contained in said second chamber through said cannula and into said first chamber; and wherein said cannula does not puncture a seal, no air is introduced into either the first chamber or the second chamber, and a combined volume of the first chamber and second chamber remains constant when moving said cannula from said inoperative position to said operative position.