52 ANATOMY OF THE LYMPHATIC SYSTEM. 



turn and pleura of all animals. They are not quite as numerous 

 to be seen on the lymphatic capillaries of the mesentery of cat, 

 monkey, and dog; but they occur relatively often in that of frog 

 and toad. They are naturally extremely short, in consequence of the 

 superficial position of the lymphatic capillaries, the membrane being 

 very thin ; but they are in every case lined by a special layer of 

 endothelium, which in every respect resembles that of those above 

 mentioned. 



In these membranes omentum, pleura mediastini and mesentery - 

 stomata vera occur on lymphatic capillaries which accompany or in- 

 vaginate the blood-vessels, as well as on those which have no such 

 relation to the blood-vessels. It is necessary to mention that these 

 stomata are generally not so very easy to demonstrate in the normal 

 omentum, pleura mediastini, and mesentery (except that of the frog 

 and toad), the lymphatic capillaries not being so easy to demon- 

 strate. If, however, these membranes are slightly affected with 

 chronic inflammation, their demonstration does not require any great 

 skill ; by spreading out the fresh membranes carefully in serum they 

 may be seen without further preparation. Exactly like the vertical 

 lymphatic canals, i.e. stomata vera, just mentioned, are those of the 

 septum cysternaB lymphatics magnse of frogs and toads, described 

 by Dogiel and Schweigger-Seidel. Different from the description 

 given by these observers, I must mention that the vertical lymphatic 

 canals are lined by a special layer of more or less polyhedral 

 endothelial cells, which consist of a granular protoplasm. Accord- 

 ing to D. and S. S., these stomata are bordered by the nuclei of the 

 common flat large endothelial plates, both on the peritoneal surface 

 and on that of the cysterna, which nuclei project into the stoma ; but 

 these projections represent that special lining layer of polyhedral 

 endothelial cells seen in profile, as it is easily to be recognised on 

 membranes carefully spread out in the fresh state, and still better 

 after staining with nitrate of silver. I refer the reader to Figure 

 3, on Plate L In female frogs and toads the endothelial lining of 

 these vertical lymphatic canals is provided with ciliae. 



female frogs and toads during the winter months I 

 fave found the endothelium of the stomata of the septum, as well as 



