A soft cannula is inserted into tissue and affixed to skin. A cannula arrangement moves within a housing and provides the soft cannula and a guiding needle extending through the cannula to temporarily stiffen it. A drive effects an insertion movement of the cannula arrangement from a first position, where a puncturing tip is pulled back relative to a face of the housing, into a second position, where the puncturing tip protrudes beyond the face, and automatically effects a retracting movement of the guiding needle into a third position, where the puncturing tip is pulled back relative to the face. The face is formed by a base plate affixed to the housing so that when the cannula arrangement is in the second position, the face detaches from the housing. A holder element is connected to the soft cannula and couples to the base plate in the cannula arrangements second position.
