Wilson, Memhrana Tympani. 463 



they enter the plexuses to be described later (Figs. 3 and 6). {b) 

 Into the same or another bundle where they may pass upward or 

 downward and soon become impossible to follow accurately (Figs. 

 3 and 5). (<r) To form a subepithelial plexus, {d) To end in the 

 subcutaneous tissue and m the epithehum. In addition we find 

 nerves which form plexuses around the blood vessels. 



The subepithelial plexus, composed of nonmedullated nerves, 

 is very intricate and into it run not only nerves from the ground 

 plexus but also nerves issuing directly from the nerve bundles. 

 In it the entering nerves may divide into fine fibrils. Some of 

 the fibers can be traced into the epithelium; others, after a long 

 course, leave the subepithelial plexus and enter again into the 

 ground plexus. Those penetrating the epithelium may do so 

 singly or in groups, running between the cells interlacing with 

 each other and ending in the upper layers in fine or bulb-like 

 points. 



In addition to the cuticular endings there are present many 

 noncapsulated tree endings (Fig. 7). There are given off from 

 the ground plexus nerve fibers of considerable diameter, which 

 break up into an arborization diflPering in no respect from tree 

 endings elsewhere, except that they are relatively smaller. They 

 sometimes interlace intricately with each other. In their course 

 they may give off nonmedullated branches which also end in 

 arborizations, and in this way one nerve fiber may distribute its 

 arborizations over a wide area. These arborizations are usually 

 subcuticular. 



Speaking generally, it may be said that the pars flaccida pre- 

 sents the picture of a membrane very rich in nerves not only 

 because of the numerous branches passing down through it, but 

 also because of its plexuses and abundant endings. 



//. The nerves of the pars tensa enter chiefly from the external 

 auditory meatus either over the pars flaccida or at the limbus. A 

 few fibers pass in directly from the tympanic cavity. 



(i) Those coming from the pars flaccida are directed toward 

 the manubrium and reach it, not as one, but as several nerve 

 bundles. These cross the plicae anterior and posterior at various 

 angles and at varying points, toward the manubrium which they 

 reach along its upper third. The place at which the larger bundles 

 cross varies in diflPerent animals — thus, in the dog and cat they 

 cross over the capitulum or the anterior plica (Figs, i and 4); in 



