A syringe (12) having: a syringe body (18) in which a passage (28) for the circulation of fluid is defined, the circulatory passage (28) being extended by a main element (20) for fluidic connection to a complementary volume (13); and a movable piston (36) inside the syringe body (18), defining, with the syringe body (18), a chamber for the containment of fluid, opening out through the circulatory passage (28). The syringe body (18) defines a closed space in which the piston (36) is movably mounted. The piston (36) also defines in the closed space an auxiliary return chamber. The syringe body (18) defines a return passage (48) opening out into the auxiliary return chamber (46). The return passage (48) is extended by an auxiliary element (50) for connection to the complementary volume (13).