THE EXTERNAL EAR. 43 



the capillaries pass more transversely or obliquely from the 

 exterior between the radial fibres to the internal plexus of the 

 mucous membrane, so that this spot appears to be the least 

 vascular part of the membrana tympanum. Towards the 

 periphery the radial fibres diverge from one another, leaving 

 grooves or channels between them that are filled by capillaries 

 which quickly increase in size ; the vessels themselves, there- 

 fore, also run in a radial direction and at regular distances from 

 each other. These vessels also pour their contents into the 

 marginal plexus. 



If the cutis and the mucous membrane be detached from the 

 membrana propria, the transversely and obliquely traversing 

 vessels are torn through, and then the above-mentioned spaces 

 with adherent nuclei come into view. 



The inner blood vascular plexus of the mucous membrane 

 consists essentially of capillaries, and is chiefly distributed as a 

 close plexus of vessels around the manubrium and about the 

 tendinous ring. The plexus of the last-named part is to be 

 regarded as a prolongation of the capillaries of the mucous 

 membrane of the tympanic cavity. These run on to the 

 membrana tympani, there form loops around or entirely encircle 

 the foramina between the trabeculse, and then turn back to the 

 vessels of the tympanic mucous membrane, or extend to the 

 borders of the tunnel -like passages, or penetrate directly into 

 the deeper layers in order to anastomose with the capillaries of 

 the membrana propria. The plexus surrounding the manu- 

 brium, and also connected with the median and the above- 

 described plexus, obtains its blood from 'a few small arteries 

 which run from above downwards in nearly the same direction 

 as the arteries of the cutis. 



As we have just seen, the blood of the tympanic mucous membrane 

 is carried off in two ways by the veins of the tympanic cavity, and by 

 those of the external auditory meatus. The chief proportion of the 

 blood traversing the arteries of the membrana tympani and the capil- 

 laries may therefore enter the larger veins by very different routes ; 

 by a shorter path into the plexus of the malleus, and by a longer path 

 over the membrana tympani into the marginal plexus. The path 

 traversed by the blood during life will obviously depend upon the 

 nature of the resistance with which it meets hi the different veins. It 



