486 



THE ORGAN OF HEARING. 



of a cat, the general relations of the .parts are clearly shown. Figure 

 373 is sketched from a longitudinal section of the cochlea of a guinea- 

 pig, and shows the appearance presented by a section through one 

 of the turns of the bony cochlear canal and its contents as seen under 

 higher maenification. We mav now proceed with a fuller consider- 



o & ^ 



ation of the structures mentioned. 



map 



Fig. 372. Longitudinal section of the cochlea of a cat ; X 2 5- This figure gives a 

 general view of the cochlea. The cochlear duct is met with six times in the section : dc t 

 cochlear duct ; gsp, spiral ganglion ; Kn, osseous cochlear wall ; hp, ligamentum spirale ; 

 msp, membrana spira is; tv, membrana vestibularis or Reissner's membrane ; , nervus 

 cochlearis ; set, scala tympani; scv, scala vestibuli (Sobotta, "Atlas and Epitome of 

 Histology"). 



The lamina spiralis ossea consists of two bony plates which in- 

 close between them the ramifications of the cochlear nerve. The 

 vestibular surface of the osseous lamina spiralis is covered by peri- 

 osteum, which is continuous with a peculiar tissue, known as Unions 

 spiralis. The latter begins at the point of attachment of Reissner's 



