A medical sheath is a medical sheath which is used for medical treatment together with a medical device having an insertion portion that can be inserted into a body cavity of a subject via a trocar and used for treatment of a test site existing in the body cavity of the subject What is claimed is: 1. A sheath comprising: a sheath body formed in a shape that can be inserted into and pulled out from an insertion hole through which an insertion portion is inserted in a trocar and a sheath body which is provided in the sheath body, A channel which is a conduit which is provided in the sheath body and guides at least one of the illumination light irradiated to the examination site and the return light emitted from the examination site in accordance with the illumination of the illumination light And an optical transmission unit for emitting light.医療用シースは、トラカールを介して被検体の体腔内に挿入可能な挿入部を有する医療用デバイスを用いて被検体の体腔内に存在する被検部位の処置を行う際に併用される医療用シースであって、トラカールにおいて挿入部が挿通される挿通孔に対して挿抜可能な形状に形成されたシース本体と、シース本体に設けられ、挿入部を挿抜可能な形状を具備するように形成された管路であるチャンネルと、シース本体に設けられ、被検部位に照射される照明光、及び、照明光の照射に応じて被検部位から発せられる戻り光のうちの少なくとも一方の光を導光するための光伝送部と、を有する。
