216 



SPECIAL SENSES. 



gular canal, called the canalis cochleae, or the membranous 

 cochlea. 



In the anatomical description of the contents of the bony 

 cochlea, the membranous parts may be designated as fol- 

 lows : 



1. The portion below the bony and membranous septum, 

 called the scala tympani. This is formed by the periosteum 

 lining that portion of the cochlea and the under surface of 

 the bony lamina, and the membrana basilaris. 



2. The scala vestibuli. This is formed by the periosteum 

 lining the corresponding portion of the bony cochlea and 



FIG. 15. 



Vertical section of the cochlea of a foetal calf, magnified six diameters. This section shows the 

 septum between the two scalae, the scala tympani below the septum, the scala vestibuli 

 above the septum, and the triangular canal externally The outer wall of the cochlea is os- 

 sified, but the modiolus is still cartilaginous. The radiating lines in the modiolus indicate 

 the course of the auditory nerves. (KOLLIKEB, Uandbuch der Gewebelehre, Leipzig, 

 1867, S. 714.) 



the upper surface of the bony septum, and is bounded ex- 

 ternally by the membrane of Reissner. 



3. The true, membranous cochlea. This is the spiral 

 triangular canal, bounded externally by the periosteum of the 

 corresponding portion of the wall of the cochlea ; internally, 

 by the membrane of Reissner ; and, on the other side, by 

 the membrana basilaris. 1 "What we thus call the membra- 



1 Some anatomists include this canal in the scala vestibuli. 

 of clearness, we describe it by itself, as a distinct canal. 



For the sake 



