Hypodermic syringe comprising: a barrel which with an inner wall thereof defines a reservoir, comprising a first section near a first end of the barrel and a second section near a second end of the barrel, a closing-off device, placed in the first section of the barrel, for closing off the first end of the barrel, wherein the closing-off device is provided with a through-opening outwardly debouching in a nozzle adapted for a coupling to a needle device, a plunger, slidably placed in the second section of the barrel, for pushing a fluid out of the barrel at penetration into the barrel, wherein the plunger at least partially protrudes out of the barrel at the second end thereof, and wherein a first end of the plunger is inserted in the barrel and comprises first coupling members, wherein the closing-off device comprises a circumferential wall that sealingly abuts the inner wall of the first section of the barrel, wherein the closing-off device at the side facing away from the nozzle is provided with a recess extending along a centre line of the closing-off device, wherein in the recess two diametrically opposite flexible first locking members are placed that extend in the longitudinal direction of the recess and towards the circumferential wall, which locking members by engaging into diametrically placed locking grooves in the inner wall lock the closing-off device against a movement in the direction from the first end to the second end, wherein the locking members at or near their end facing away from the nozzle comprise second coupling members for coupling to the first coupling members, characterized in that the recess extends over the full width of the closing-off device, which recess in the direction of the nozzle merges into the through-opening, and wherein the closing-off device at the side facing away from the nozzle, at a circumferential part of the closing-off device that is situated outside of the recess, is provided with two diametrically opposite blocking members that extend substantially parallel to the centre line of the closing-off device and extend radially outward, which blocking members by engaging into diametrically placed blocking grooves in the inner wall of the barrel lock the closing-off device against a movement in the direction from the second end of the barrel to the first end of the barrel. a barrel which with an inner wall thereof defines a reservoir, comprising a first section near a first end of the barrel and a second section near a second end of the barrel, a closing-off device, placed in the first section of the barrel, for closing off the first end of the barrel, wherein the closing-off device is provided with a through-opening outwardly debouching in a nozzle adapted for a coupling to a needle device, a plunger, slidably placed in the second section of the barrel, for pushing a fluid out of the barrel at penetration into the barrel, wherein the plunger at least partially protrudes out of the barrel at the second end thereof, and wherein a first end of the plunger is inserted in the barrel and comprises first coupling members, wherein the closing-off device comprises a circumferential wall that sealingly abuts the inner wall of the first section of the barrel, wherein the closing-off device at the side facing away from the nozzle is provided with a recess extending along a centre line of the closing-off device, wherein in the recess two diametrically opposite flexible first locking members are placed that extend in the longitudinal direction of the recess and towards the circumferential wall, which locking members by engaging into diametrically placed locking grooves in the inner wall lock the closing-off device against a movement in the direction from the first end to the second end, wherein the locking members at or near their end facing away from the nozzle comprise second coupling members for coupling to the first coupling members, characterized in that the recess extends over the full width of the closing-off device, which recess in the direction of the nozzle merges into the through-opening, and wherein the closing-off device at the side facing away from the nozzle, at a circumferential part of the closing-off device that is situated outside of the recess, is provided with two diametrically opposite blocking members that extend substantially parallel to the centre line of the closing-off device and extend radially outward, which blocking members by engaging into diametrically placed blocking grooves in the inner wall of the barrel lock the closing-off device against a movement in the direction from the second end of the barrel to the first end of the barrel.