on the Membrana Tympani. 5 



it under the most favourable circumstances; but, when these 

 are attended to, it can be perceived without the aid of glasses. 



If the membrana tympani of the human ear is completely 

 exposed on both sides, by removing the contiguous parts, and 

 the cuticular covering is carefully washed off from its external 

 surface, then, by placing it in a clear light, the radiated direc- 

 tion of its fibres may be easily detected. If a common magnify- 

 ing glass is used, they are rendered nearly as distinct as those 

 of the elephant appear to the naked eye ; their course is exactly 

 the same ; and they differ in nothing but in being formed upon 

 a smaller scale. 



When viewed in a microscope magnifying 23 times, the 

 muscular fibres are beautifully conspicuous, and appear uni- 

 formly the same throughout the whole surface, there being no 

 central tendons, as in the diaphragm ; the muscular fibres ap- 

 pear only to form the internal layer of the membrane, and are 

 most distinctly seen when viewed on that side. 



In examining this membrane in different subjects, the parts 

 were frequently found in a more or less morbid state. In one 

 instance, the membrane was found loaded with blood-vessels, 

 was less transparent than usual, and was united by close adhe- 

 sion to the point of the long process of the incus. In another 

 instance, there was a preternatural ossification adhering to it, at 

 a small distance from the end of the handle of the malleus. 



As muscles in general are supplied with blood-vessels in pro- 

 portion to the frequency of their action, it is an object of im- 

 portance to determine the vascularity of the membrana tympani. 

 Upon this subject, my own want of information has been amply 

 supplied by Dr. Baillie, who, in a communication upon this 

 subject, showed me a preparation of the membrane, in which 



