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



layer that presents the same relations to the periosteum as 

 those that have been above more minutely detailed. The 

 principal nerve trunks exhibit at certain points deep con- 

 strictions/ caused by highly retractile bands, whilst at others 

 they form fusiform enlargements. Ganglion cells are distri- 

 buted, often in considerable numbers, both in and on the 

 trunks. I found such ganglion-bearing trunks lying close 

 beneath the epithelium, where the cells are columnar, and 

 show the forms mentioned above. These columnar cells are 

 prolonged into slender processes that run towards the nerves, 

 and may be traced into their sheaths, but I am unable to give 

 their further relations. 



The nerves themselves exhibit remarkable relations in 

 another point of view. I have been able to demonstrate by 

 injection the presence of capillary bloodvessels, which form, 

 both in the nerve sheaths and amongst the nerve fibres them- 

 selves, a narrow-meshed basket-like plexus that may also be 

 rendered apparent by the chloride of gold method. If injected 

 preparations, after previous hardening in alcohol, be treated 

 with solution of chloride of gold, a second system of tubes 

 becomes visible under favourable circumstances, which is not 

 filled with the injection. This usually accompanies the nerve 

 sheaths, or even lies in their substance, and is distinguishable 

 from the blood vascular system by the presence of the sphe- 

 roidal and fusiform enlargements that are characteristic of the 

 lymphatics. I have succeeded in following branches of this 

 system through the nerve sheaths as far as to the nerve fibres, 

 but have been unable to trace their ultimate distribution in 

 the interior of the nerves. 



The statements of v. Troeltsch (44), respecting the .presence 

 of mucous glands in the tympanic cavity of Man, have up to 

 the present time remained uncorroborated, though I can sub- 

 stantiate their existence in Dogs and Cats, where they form 

 simple follicles lined by columnar epithelium. 



As the further relations of the nerves and lymphatics in 

 these animals are precisely similar to those of Man, I need 

 only add a few remarks on the mucous membrane of the bulla 

 ossea. The membrane here alters its characters ; the medul- 

 lated nerve fibres become fewer in number, and ganglion cells 



