XXVIII.] THE EAR. 299 



is not easy, and the arrangement differs but 

 little from that in the skate. 



13. Take the cochlea of a mammal, preferably of a 

 guinea-pig, which has been treated with picric 

 acid until the salts have been dissolved out, and 

 subsequently with alcohol. Remove all the 

 softened bone as close as possible to the cochlea. 

 Slice away the apex of the cochlea, stain the 

 remainder with hsematoxyhn and imbed in the 

 manner given in Lesson xx. § 6. Cut sections 

 through the axis of the cochlea, throw away the 

 first two or three and the last two or three 

 sections ; clear the rest on a slide with creosote 

 and turpentine, mount in Canada balsam. 

 Observe 



a. The division of each turn of the cochlea into 

 three canals by the basilar membrane 

 running across from the end of the lamina 

 spiralis, and by the membrane of Reissner 

 starting from the lamina farther back • the 

 latter will very probably have been torn 

 through. 



h. The following modifications of the epithelium 

 cells of the scala media, starting from the 

 inner side of the basilar membrane, 

 a. Cells passing from cubical to columnar. 

 /3. The single inner hair cell, columnar 

 with short rod-like processes, the so- 

 called hairs, from its free surface, its 

 deep pointed end is more or less hidden 

 by small cells with large nuclei. 



