XX TI1K 1 AR AM) nil. SI.NSi: OF HKAKINV, 225 



project into the endolymph. The fibres of the auditory nerve 

 end by breaking up into a network of fine fibrils lying among 

 and in close contact with the cells. 



The Cochlea. Somewhat as the utricle gives off the semi- 

 circular canals, so the saccule gives off a canal containing also 

 endolymph, called the canal of the cochlea. This canal does 

 not, however, return to the saccule as a semicircular canal 

 returns to the utricle, but has a blind end. It is, moreover, 

 coiled in the form of a spiral of two and a half turns, forming a 

 small cone called the cochlea. It lies in a spiral canal in the 

 bone, but is not merely loosely 

 attached here and there to the 

 wall of the cavity as are the semi- 

 circular canals, but closely fixed 

 all the way along to the outer 

 wall of the spiral cavity, and also 

 to a ledge of bone projecting in- 

 wards from the inner wall or wall 

 next the axis of the spiral. By 

 these attachments of the canal of 

 the cochlea the cavity in the bone FlG '7--A section through the axU 



,. ., , . of the cochlea. . 



is divided into two parts, one 



. . , , / , - Ma, the bony axis ; Sc.Af, canal of 



above and one below the canal of cochlea; Jf>| , the part of lhc 



the cochlea, which Only COmmuni- <bony cavity above the canal of 



cate with one another at the end he cochlea Sc. r, the part below ; 

 of the cavity, that is, at the top '-* ** s P iral % P"*""'* 



. , f i from the axis; C.N, branch of 



of the spiral after the canal of the auditory nerve, 

 cochlea has ended. Both parts of 



the cavity contain perilymph. If the part of the cavity which lies 

 above the canal of the cochlea is traced down the spiral it is 

 found to be continuous with the cavity in which the saccule, 

 utricle, and semicircular canals lie, and so leads to the fenestra 

 ovalis. The cavity below the canal of the cochlea leads to the 

 fenestra rotunda, where it is separated by membrane from the 

 cavity of the middle ear. We thus see how the fenestra rotunda 

 and the fenestra ovalis lie in the wall of one and the same 

 cavity, although this cavity is of a very complicated shape, 

 and the passage from one fenestra to the other is a very 

 roundabout one. 



The canal of the cochlea is not round but triangular in 



Q 



