44 THE EXTERNAL AND MIDDLE EAR, BY J. KESSEL. 



may however be said with certainty that the arterial blood always 

 returns by the shortest route through the plexus around the manu- 

 brium, when no special obstacle is presented to its course, in the veins 

 into which the vessels of this plexus discharge themselves (Prussak, 37). 

 I have satisfied myself of the accuracy of this last statement, which 

 was advanced by Prussak from the results of his carefully performed 

 injection experiments. As I cannot here enter into any details re- 

 specting the means and methods which have led me to this conclusion, 

 I shall content myself with a statement of the method I have employed 

 to demonstrate the circulation of the membrana tympani. I subjected 

 frogs to the influence of woorara, and having divided the masseters, drew 

 back the lower jaw as far as possible. The animal was then so placed 

 between moist cushions upon a glass plate, that the external surface 

 of the membrana tympani to be examined lay upon the plate, and was 

 then pinned down to the stage of the microscope. Owing to the short 

 and wide Eustachian tube of the Frog, the circulation of the various 

 portions of the membrana tympani may then, by judicious turning of 

 the head, be very well studied. 



In regard to the lymphatics it may be broadly stated that, 

 like the bloodvessels, they are arranged in three layers. The 

 first belongs to the cuticular investment ; the second to the 

 membrana propria ; and the third to the mucous membrane. 

 In the cutis they form an extremely fine plexus lying imme- 

 diately beneath the rete Malpighii, the vessels of which 

 accompany and frequently arch over the blood capillaries. 

 They gradually pass into wider capillaries, which often cross 

 the blood capillaries, and ultimately collect into separate 

 larger trunks, which either run backwards and upwards, or 

 extend like the bloodvessels at various parts towards the peri- 

 phery and the auditory meatus. In the mucous membrane a 

 sparingly distributed subepithelial plexus is found chiefly in the 

 vicinity of the tendinous ring, which is distinguishable from 

 the bloodvessels of equal width by its manifold, dilatations. 

 The vessels penetrate into the lacunar system through the 

 above-described spaces in the fibrous framework, and there 

 form large spherical and saccular dilatations. (See fig. 282.) 



These last again are continuous with capillaries of small 

 diameter presenting valve-like constrictions, which either com- 

 municate with the above-mentioned deeper-lying funnel-shaped 



