A syringe (1) comprises: a syringe external cylinder (2) further comprising an external cylinder main body (21), a reduced diameter part (22) which is disposed on the leading end part of the external cylinder main body (21), and a lock adapter (6) which is positioned concentrically about the external circumference part of the reduced diameter part (22) and a cap (5), further comprising a cap main body (7) which is mounted upon the syringe external cylinder (2), and which, in a mounting state, watertightly seals the reduced diameter part (22), a mounting part (8) which is positioned at the base end side of the cap main body (7), and which is mounted upon the external circumference part of the lock adapter (6), and a fracture part (9) which links the cap main body (7) and the mounting part (8), and with which the linkage may be disengaged by fracturing. The cap main body (7) further comprises an inner ring (74) and an outer ring (75) which are formed protruding on the base end side, and which are positioned concentrically. In the mounting state, the inner ring (74) is located between the reduced diameter (22) and the lock adapter (6) in a detachably engaged state, and the outer ring (75) is located on the outside of the lock adapter (6) in a detachably engaged state.Linvention concerne une seringue (1), qui comprend : un cylindre externe de seringue (2) comprenant en outre un corps principal de seringue externe (21), une partie à diamètre réduit (22) qui est disposée sur la partie terminale avant du corps principal du cylindre externe (21), et un adaptateur de verrouillage (6) qui est placé en position concentrique autour de la partie de circonférence externe de la partie à diamètre réduit (22) et un bouchon (5) qui comprend en outre un corps principal de bouchon (7) qui est monté sur le cylindre externe de seringue (2) et qui, à létat monté, scelle avec étanchéité à leau la partie à diamètre réduit (22), une partie de montage (8) qui est placée du côté terminal de l
