308 THE LYMPHATIC SYSTEM, BY F. v. EECKLINGHAUSEN. 



are immediately placed, but sometimes they are situated some- 

 what obliquely, towards the margin of the vessel, or they may 

 even be as far distant as a semi-diameter of the vessel, in 

 which case there is an oblique canal leading to the latter. 



The openings (stomata) never exceed the size of an epithelial 

 cell. The rich lymphatic plexus of the central tendon with 

 these large stomata is obviously subservient to the absorption 

 of the fluids of the peritoneal cavity, which, like the lymph, 

 contains contractile cells, capable, from their size, of passing 

 through the stomata. In the frog, which has no diaphragm, 

 Schweigger-Seidel and Dogiel found that openings of a similar 

 nature exist in that surface of the wall of the cisterna lym- 

 phatica magna that is turned towards the abdominal cavity. 

 Dybskowskyalso was able, by causing the absorption of coloured 

 fluids from the pleural cavity of dogs into the lymphatic plexus 

 of the pleura, to demonstrate the existence of similar openings 

 between the epithelial cells. From these experiments we may 

 now reasonably expect that analogous formations will be found 

 in the pericardium and in the arachnoid membrane of the brain, 

 and that, consequently, we may conclude all serous cavities to 

 possess a very intimate connection with the lymphatic system. 



Further, it has been shown, in regard to many epithelial layers, 

 ven in parts where the lymphatics certainly do not approximate 

 the surface, that when they have been treated with nitrate of 

 silver, sharply defined spaces exist between the epithelial cells 

 which may be placed in the same category with the stomata 

 above described. Oedmansson first described them in the epi- 

 thelia of serous membranes. He drew attention to their occur- 

 rence in the epithelial stratum of the chyle vessels and of the 

 follicles of Peyer ; Ludwig, Schweigger-Seidel, and Dybskowsky 

 demonstrated their presence in the pleura and peritoneum, and 

 further showed that they were especially abundant in the 

 small-celled epithelium which lies directly over the lymph 

 vessels on the peritoneal surface of the central tendon of the 

 diaphragm. They are distinguished from the proper stomata 

 by their much smaller size, the largest only attaining the 

 diameter of a red blood corpuscle, and they are principally 

 found at the points of junction of several epithelial cells. I 

 recognised these spaces when I first began to employ silver as 



