Does the endolymph pass through the base of the cupula?

Whether the endolymph of the semicircular canal passes the cupular partitio n or not was examined using the lateral semicircular canal system of adult pigeons (Columba livia). By applying various pressures by means of injectio n of a dye solution through the membranous canal, it was found that the dye solution,was seen to pass the cupula even under very low pressures when th e pressure was increased gradually. When pulled by a magnet, the ultrafine particles of the dextran magnetite contained in the injected fluid were fou nd to pass through the subcupular space without evident increase of the amp ullary pressure. (C) 2001 Published by Elsevier Science Ltd.