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 magnification. We may now proceed with a fuller consider- 

 ation of the structures mentioned. 



gsp 



Kn 



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

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

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

 msp, membrana spiralis; mv, 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 limbus 

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



