MEMBKANA TYMPANI. 199 



The color of the membrana tympani, when it is examined 

 with an aural speculum by daylight, is peculiar, and rather 

 difficult to describe, as it varies in the normal ear in different 

 individuals. Politzer describes the membrane, examined in 

 this way, as translucent, and of a color which " most nearly 

 approaches a neutral gray, mingled with a weaker tint of vio- 

 let and light yellowish-brown." l This color is modified, in 

 certain portions of the membrane, by. the chorda tympani 

 and the bones of the ear, which produce some opacity. The 

 entire membrane in health has a soft lustre. In addition, 

 there is seen, with proper illumination, a well-marked, trian- 

 gular cone of light, with its apex at the end of the handle of 

 the malleus, spreading out in a downward and forward direc- 

 tion, and from ^ to T ^ of an inch broad at its base. This 

 appearance is regarded by pathologists as very important, as 

 indicating a normal condition of the membrane. It is un- 

 doubtedly due to reflection of light, depending upon three 

 factors, indicated by Roosa as follows : " First, the inclina- 

 tion of the membrana tympani to the auditory canal ; second, 

 the traction of the malleus, which renders it concave at the 

 centre ; third, its polish or brilliancy." 2 With this explana- 

 tion, it is not admitted that the light spot is due to a peculiar 

 structure of that portion of the membrane upon which it is 

 seen. 



Uses of the Membrana Tympani. It is unquestionable 

 that the membrana tympani is very important in audition. 

 In cases of disease, in which the membrane is thickened, per- 

 forated, or destroyed, the acuteness of hearing is always more 

 or less affected. That this is in great part due to the absence 

 of a vibrating surface for the reception of waves of sound, is 

 shown by the relief which is experienced by those patients 

 who can tolerate the presence of an artificial membrane of 



1 POLITZER, The Membrana Tympani in Health and Disease, New York, 

 1869, p. 23. 



* ROOSA, Diseases of the Ear, Xew York, 1873, p. 189. 



