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6 ' ANATOMY OF THE LYMPHATIC SYSTEM. 



of the cell ; the cell possesses in some cases a more or less distinct 

 constriction between the two nuclei, and the cilia of the surface have 

 become very delicate and short. 



Finally, there may be seen endothelial cells without cilia, which 

 consist of two nearly spherical portions held together by a short neck ; 

 each portion possesses a spherical, sharp-outlined nucleus, with clear 

 contents and a shining nucleolus. 



Mr. Francis Darwin showed to me a preparation of the mesogas- 

 trium of Rana temporaries, where there were to be seen germinating 

 endothelial cells that perform distinct amoeboid movements. Fig. 52 

 shows such young endothelial cells, which bud from a freely-projecting 

 knob ; the cells are in amoeboid movement. 



A similar, but not quite so abundant, germination may be observed 

 on the peritoneal surface of the septum cisterns lymphaticae magnse 

 of the frog, especially on the endothelial cells which surround, or 

 more correctly speaking, which line the stomata first described by 

 Dogiel and Schweigger-Seidel. 



These authors found on the peritoneal surface of the septum of 

 female frogs, during the spawning season, ciliated endothelial cells of 

 a nearly cylindrical shape, in small groups near the stomata. I shall 

 turn to the stomata afterwards. At present I wish only to mention 

 that during the winter months, in some septa besides the germinating 

 mostly ciliated endothelial cells, there exist shorter or longer tracts, 

 .which project more or less freely on the peritoneal surface, and which 

 are covered with polyhedral, sometimes ciliated endothelial cells. 



Ludwig and Schweigger-Seidel first called attention to the differ- 

 ence which exists as regards the endothelium of different portions of 

 the peritoneal surface of the centrum tendineum of the diaphragm of 

 rabbits. These authors have shown that the endothelial cells, which 

 are situated over the straight lymphatic channels, between the tendon 

 bundles, are of a smaller size than the endothelial cells which lie over 

 the tendon bundles themselves. 



They assert also that there exist sometimes groups of lymphoid 

 corpuscles, which are continuous with, or properly speaking, derived 

 from, those stripes of small endothelial cells previously mentioned. 

 I am able not only to confirm this latter observation, but also to 



