Abstract: The inserting means comprises a flexible insertion part (14) adapted to be pushed into an object to be examined, especially the human colon (60) and including, between an inner wall (16) and an outer wall (18), an intermediate space (20) sealed towards the outside. The outer wall (18) is formed by a flexible hose which, however, cannot be inflated like a balloon by the fluid in the intermediate space (20). The inner wall (16) of the insertion part (14) likewise is formed by a hose; the latter is deformable radially inwardly by fluid introduced into the intermediate space (20) and can be caused to lie against the outer wall (18) by evacuation of the intermediate space (20). The insertion part (14) can be rendered rigid in any desired position by evacuating the intermediate space (20). It is easy to insert the corresponding instrument, e.g. the colonoscope into the object to be examined through the insertion part (14) thus fixed.