224 



PHYSIOLOGY FOR BEGINNERS 



CHAP. 



labyrinth, the bony cavity in which they lie being the osse- 

 ous labyrinth. The membraneous labyrinth contains a fluid 

 called the endolymph. 



One end of each semicircular canal is enlarged to a small 

 bulb, and is here closely fixed to the bone ; for it is at this 

 spot that fibres of the auditory nerve pass to the mem- 

 brane, and end in it in a small patch. Other branches of 

 the auditory nerve end in similar patches in the membrane 

 of the utricle and in that of the saccule. The membrane 



FIG. 106. Section lengthwise through the dilated end of a semicircular canal. 

 i , part leading to the canal ; u, part leading to the utricle ; e, ordinary epithelium 

 lining the greater part of the canal ; c.r, crest or patch of auditory epithelium, 

 a.e ; /, intermediate epithelium; aJi, auditory hairs; c.t, connective tissue; 

 n, fibres of auditory nerve. 



itself consists of fibrous connective tissue lined internally by 

 an epithelium consisting of a layer of cubical cells. At the 

 patches where the auditory nerve ends the membrane is much 

 thicker, and the epithelium is specially modified for the recep- 

 tion of sound vibrations. This part is known as the auditory 

 epithelium. 



The auditory epithelium consists of several layers of cells. 

 All these cells are very delicate, and while some are cylindrical 

 in form, others are spindle-shaped. From the surface of the 

 epithelium stiff hair-like processes connected with the cells 



