THE EXTERNAL EAR. 33 



normal, is positively denied by Hyrtl (16) and others, who regard it 

 as a consequence of inflammation. I have satisfied myself, in company 

 with Dr. Gruber, of its occurrence both in the dead body, and also 

 directly during life. 



After this general account of the topographical relations of 

 the membrana tympani, I proceed to the description of its 

 finer microscopical characters. 



The cutis of the bony meatus is continued upon the mem- 

 brana tympani at all points of its circumference. The small 

 hairs and glands sparingly present in the cutis are entirely 

 absent over the membrana tympani ; the papillse extend only 

 to the tendinous ring, except in the posterior superior part, 

 where they reach as far as to the processus brevis. The rete 

 Malpighii in the remaining segments of the membrana tym- 

 pani exhibits a plane and only here and there wavy course. In 

 a fresh membrana tympani, treated with perosmic acid, the 

 corneal layer, just as in the meatus externus, becomes stained 

 of a black colour precisely as far as to the epidermic layer of 

 cells (a proof of the fatty nature of their ceruminous con- 

 tents Williams). The corneal cells and variously thick cuticle, 

 as well as the corium, gradually diminish in thickness from the 

 periphery towards the handle of the malleus, but attain their 

 greatest thickness over its external edge. This is caused by 

 the circumstance that the vessels and nerves of the cutis and 

 of the membrana propria, accompanied by strong bands of 

 connective tissue, extend towards the handle of the malleus in 

 an oblique direction from the posterior and superior wall of 

 the auditory meatus, and having reached it, cover it. Part 

 of the bands of connective tissue encircles the handle of the 

 malleus, and joins on the anterior side with that which invests 

 the ascending veins of the malleal plexus. 



Independently of the just-described general characters of the 

 membrana tympani, the thickness of the epidermis is subject to mani- 

 fold individual variations. It is a fact of general experience that the 

 cells of the horny layer quickly become cloudy, and readily separate 

 after death, so that in many instances we are not in a position to 

 determine whether we have still all the layers before us, or whether 



VOL. III. D 



