THE EXTERNAL EAR. 47 



beneath the cuticle of the derails and the epithelium of the 

 mucous membrane. We may thus distinguish here a basal, a 

 capillary, and a subepithelial plexus. 



A principal nerve trunk, which consists of medullated fibres 

 provided with the sheath of Schwann, and lies between the 

 cutis and the membrana propria, passes from the auditory 

 meatus to the membrane at the upper part of the posterior 

 segment close to and behind the artery, giving off branches 



Fig. 283. 



Fig. 283. Serous canals of the membrana tympani of the Dog. 



which accompany the vascular twigs. In correspondence with 

 the forking of the artery over the manubrium of the malleus, 

 the nerve divides into two branches, of which one supplies the 

 anterior, and the other the posterior and lower part of the 

 membrana tympani. Besides this main trunk, several smaller 

 nerves accompany vessels passing to the membrane from various 

 parts of the periphery. The coarse branches of all these nerves 

 which lie between the cutis and membrana propria, I have 

 named the "fundamental plexus of the membrana tympani." 



The branches given off from the trunks break up into 

 numerous fibres, which, though non-medullated, are yet pro- 

 vided with sheaths, and these form wide plexuses around the 



