THE EXTERNAL EAR. 35 



" as a deep layer of the curium favourably arranged and meta- 

 morphosed for physiological purposes." We may also see, in 

 sections of the membrana tympani of adults, how the highly 

 refractile fasciculi radiate out, and are continuous with the thin 

 layer of fibrillar tissue of the cutis, and with the matrix of the 

 mucous membrane. In consequence of the intimate connection 

 of the fibrils by their cement, and their arrangement into 

 strong broad bands, the latter offer a strong resistance to ex- 

 tension, and form, in the mode hereafter to be mentioned, an 

 almost inextensible membrane, which as a mechanical arrange- 

 ment for auditory purposes is, as Helmholtz (11) has shown, 

 of the greatest importance. These fibres run in the several 

 already mentioned layers, either parallel to one another, or 

 decussating at very acute angles, and frequently communicate 

 (Gerlach, 7), leaving everywhere lacunae and larger spaces 

 between them. 



The lacunae are usually empty, and are then bright and 

 clear, or are covered at their borders with finely granular 

 material. Sometimes nerve cells, in addition to the nerve 

 fibres hereafter to be described, may be seen within them, 

 exactly filling their cavities. These cells, called by v. Troeltsch 

 (44) "tympanic membrane corpuscles," appear, according to 

 the plane in which they are seen, sometimes in the form of 

 fusiform, sometimes of stellate, bodies ; in the former case being 

 seen in profile, in the latter in face. 



The larger lacunae have nuclei attached to their walls, and 

 are frequently filled with amoeboid cells. By means of injec- 

 tions and the chloride of gold method, it may be demonstrated 

 that such appearances are due to transversely and obliquely 

 divided bloodvessels. 



Near the periphery of the membrane the three layers of the 

 membrana propria interweave with one another, leaving 

 variously sized spaces for the passage of vessels between them, 

 and by their further connection with the tissues of the cutis, 

 of the external auditory meatus, and of the mucous membrane 

 lining the tympanic cavity, form a thick swelling, " the ten- 

 dinous ring," which is attached to the annulus tyrnpanicus by 

 means of a thin layer of periosteum. Between the highly 

 refracting fasciculi of fibrils are found, besides the vessels, 



D 2 



