612 



THE EAR 





tened epithelium. The chorium is closely attached to the perios- 

 teum of the bony wall, the periosteum also serving as a vascular 



layer of the mucosa in the 

 mastoid cells, as well as in 

 the general tympanic cavity. 

 The tympanic membrane 

 is a thin delicate partition 

 which is formed by a reflec- 

 tion of the cutaneous layer 

 of the external auditory 

 canal on the one hand, the 

 tympanic mucosa on the 

 other, and between these 

 two membranes a layer of 

 dense fibrous tissue whose 

 tendinous bands are disposed 

 in radial and circular direc- 

 tions. The margin of the 

 tympanic membrane is in- 

 serted into a fibro-cartilagi- 

 nous ring which rests upon 

 a bony elevation, the an- 

 nulus tympanicus. 



The slender manubrium 

 or handle of the malleus 

 projects from the superior 

 margin of the ring and is 

 inserted between the folds 

 of the tympanic membrane, 

 extending downward to 



FIG. 445. TKANSECTION OF THE TYMPANIC MEM- about the Center of the 



BRANE OF A CHILD. membrane, at which point 



a, ' fibre-cartilaginous ring; 6 6' bone; c,c', ig the deepest part O f its 

 skin of the external auditory canal; d, d, tympanic A . ~ 



mucosa; e, cutaneous layer of the tympanic mu- Concavity, its Umt)0. Ihe 



cosa ; /, fibrous layer, obliquely cut at /; g, layer bony handle of the malleus, 



derived from the tympanic mucosa; h, handle of i . h p 4. wppT1 f v, p pn fa ~ pm , 



the malleus; i, blood vessels. Hematoxylin and 1 ? IU S between tne CUtaneO 



eosin. x ii. (After Kolliker.) and mucous layers of the 



tympanic membrane, is cov- 

 ered by a thin cartilaginous layer, and receives the insertions of the 

 tendinous fibres. These fibres are divisible into an outer radial 

 layer which extends from the fibro-cartilaginous ring at the periph- 



