362 MANUAL OF HISTOLOGY. 



layer which were provided with cilia upon their free surface. 

 This can be best understood by a study of Figs. 160 and 161. 

 In man the arrangement,' as well as can be followed, is almost 

 identical with that of fishes. 



TJie cocJdea. There is no easy method of obtaining good 

 preparations of the cochlea, but that by which the best results 

 have been obtained is as follows : The portion of the temporal 

 bone containing the internal ear from a recently killed animal 

 (young cat, dog, or bat) is hardened for twenty-four hours in 

 J to 1 per cent, solution of osmic acid in distilled water, 

 then placed in Muller's fluid for a week, and decalcified by a 

 0.01 per cent, solution of chloride of palladium. After decal- 

 cification it is to be washed in distilled water for a few minutes, 

 then soaked for twenty-four hours in a concentrated aqueous' 

 solution of pure gum arabic, and finally placed directly in 

 strong alcohol for twenty-four hours. After this hardening the 

 preparations are ready to be embedded in soap or hardened 

 liver, and cut. The razor is to be kept well wet with alcohol 

 while cutting. The sections are to be placed directly upon a 

 slide, and the gum removed by passing a stream of distilled 

 water under the covering-glass. 



Small portions of the lamina spiralis can also be taken from 

 the fresh cochlea, after opening it carefully with the bone-for- 

 ceps, and placed in the vapor of osmic acid or in a to 1 per 

 cent, solution of the same for a few (twelve 'to twenty-four) 

 hours. The preparations thus treated may be teased in gly- 

 cerine, and the separate cells obtained. 



The sections are to be made in a direction parallel with the 

 long axis of the cochlea, and if the central shaft (modiolus) is 

 cut through, the following picture will be presented : On each 

 side of the modiolus are seen sections of the canal of the coch- 

 lea, divided by a thin partition (the lamina spiralis, Fig. 162, 

 L sp) into an upper portion (the scala vestibuli, Fig. 162, SV) 

 and a lower (the scala tympani, Fig. 162, ST). The scala ves- 

 tibuli is further subdivided by means of a delicate membrane, 

 named after its discoverer the membrane of Reissner (Fig. 162, 

 ft /i)> which passes off at an angle from the middle of the 

 lamina spiralis and is inserted into the wall of the cochlea. 

 The portion of the canal thus cut off forms the ductus cochle- 

 aris (Fig. 162, e, e t ), and in it lies the peculiar body in which 

 the nerve terminates, and which is called the organ of Corti. 



