Reagent dispenser

Claim 1

In combination with a standard syringe including a barrel member provided with finger grips, a constricted open end and a discharge end, a piston slidably arranged in the barrel, and a piston rod having a cross-shaped cross section and connected to the piston and arranged extending through the open end of the barrel, the open end being substantially larger than the cross section of the piston rod and a gap formed between the open end and the rod, a flange being provided on an end of the rod extending out of the barrel, and an annular recess being provided in the constricted open end adjacent the finger grips and arranged facing the flange; a coiled compression spring being arranged with coils of the spring around the rod and seated between the flange and the recess in the constricted open end of the barrel for biasing the rod and piston toward the open end; and a sleeve arranged in the barrel between the open end of the barrel and the piston for limiting movement of the piston toward the open end of the barrel, the sleeve being a split sleeve formed by a sheet having a thickness less than the gap between the piston rod and open end, and bent to close on itself and of a size which is less than the size of the constricted open end for permitting passage of the sleeve through the constricted open end and into the barrel, the constricted open end and the bias of the sleeve against the barrel causing the sleeve to be retained inside the barrel abutting the constricted end.