The canula has a protective housing (102) which consists of two sections plugged into each other, wherein an inner housing (2a) has a lamella pair, and an outer housing (11) which encloses the inner housing is formed as a sleeve which is less elastic with regard to the inner housing. The outer housing has contact faces which with external pressure on oppositely disposed complementary contact faces of the inner housing initiate a closing force directed upon the funnel slot.
