THE MIDDLE EAR 



609 



men ted and fatty secretion of the glands, contains desquamated 

 epithelial cells and occasional fine hairs, together with foreign par- 

 ticles of a very varied sort. 



In the bony portion of the canal the corium or derma is firmly 

 adherent to the periosteum of the bone, and all the layers of the 

 skin are much reduced in thickness. The scanty hairs are very 

 fine, and, with the glands, are continued inward to the tympanic 

 membrane only in the superior portion of the wall of the canal. 



FIG. 443. FROM THE EXTERNAL AUDITORY CANAL OF MAN. 



o, sebaceous gland ; 6, ceruminous gland ; c, cartilage. Hematoxylin and eosin. x 15. 



(After Sobotta.) 



Papillae are present as far as the margin of the drum membrane. 

 Upon the surface of the tympanic or drum membrane, which closes 

 the inner end of the external auditory canal and separates it from 

 the cavity of the middle ear, the skin is reduced to an extremely 

 thin cutaneous coat, devoid of hairs, glands, and papillae. 



4f 



THE MIDDLE EAR 



The middle ear or tympanum is an irregular cavity, broad 

 above and behind, narrow below and in front, which lies just 

 40 



