An insertion body has: a base which is disposed along the center axis a rotation body which is disposed on the outer periphery of the base so as to be capable of rotating about the center axis relative to the base and which is configured in such a manner that the rotation about the longitudinal axis, of the rotational force transmission section of a rotational force transmission unit disposed on the inside of the insertion body can rotate a rotation unit disposed on the outside of the insertion body and a channel which has a guide section provided to the base and capable of guiding the rotational force transmission section between a first position at which the longitudinal axis of the rotational force transmission section can be tilted relative to the center axis when inserting the rotational force transmission unit from the outside to the inside of the insertion body, and a second position at which the longitudinal axis of the rotational force transmission section is parallel to the center axis and at which rotational force can be transmitted from the rotational force transmission section to the rotation body, the channel allowing the rotational force transmission unit to be inserted therethrough through the opening end at the front end of the channel.Linvention concerne un corps dinsertion qui comporte : une base, placée le long de laxe central un corps rotatif, placé sur la périphérie extérieure de la base de manière à pouvoir tourner autour de laxe central par rapport à la base, et conçu de sorte que la rotation, autour de laxe longitudinal, de la partie transmission de force de rotation dune unité de transmission de force de rotation placée à lintérieur du corps dinsertion, permet de faire tourner une unité rotative placée à lextérieur du corps dinsertion et un canal, qui comporte une partie guide, formée sur la base et permettant de guider la partie transmission de force de rotation entre une première position, dans laquelle laxe longitudinal de la partie tr
