230 



Organ of Hearing. 



Manubriiim mallei 



312. The Membrana tympani, from the outside, after partial 

 removal of the bony meatus. 



The Membrana tympani is situated 

 between the external meatus and cavity 

 of the tympanum, and is directed ob- 

 liquely inwards and downwards ; its 

 external surface appears concave, its 

 internal surface connex, and its form 

 is oval. The most depressed part of 

 the outer surface, corresponding to the 

 end of the handle of the malleus, is 

 called Umbo. At the upper and anterior 



cula auditus 01 a child, 



f ,-, . part the short process of the mal- 



trom the inner side. 



leus projects; the handle of the 



malleus is visible in its entire length ; exceptionally also the long pro- 

 cess o f t h e incus. The Membrana tympani is composed of three layers: 

 the external is derived from the integument lining the meatus; the 

 middle consists of fibrous and elastic tissues; the internal is the 

 mucous membrane. 



313. The Membrana 

 tympani and the Ossi- 



