Chap, xi.] THE LYMPHATIC VESSELS. 



8 9 



cysts lined with ciliated endothelium are sometimes 

 found. Behind the peritoneal cavity of the frog, 

 on each side of the vertebral column, exists a similar 

 large lymph sinus, called the cisterna lymphatica 

 mugna. 



116. In all instances these cavities are in direct 

 communication with 



the lymphatics of the 

 surrounding parts by 

 holes or open mouths 

 (stomata), of ten lined 

 by a special layer of 

 polyhedral endothe- 

 lial cells germinat- 

 ing cells (Figs. 54, 

 55). Such stomata 

 are numerous on the 

 peritoneal surface of 

 the central tendon of 

 the diaphragm, in 

 which are found 

 straight lymph chan 

 nels between the 



tendon bundles, and these channels communicate here 

 and there with the free surface by stomata. A 

 similar arrangement exists on the costal pleura, the 

 oinentum, and the cisterna lymphatica magna of the 

 frog. (See Chapter IY.) 



117. The serous membranes consist of endo- 

 thelium upon a layer of fibrous tissue with networks 

 of fine elastic fibres ; they contain networks of blood 

 capillaries and numerous lymphatic vessels arranged in 

 (superficial and deep) plexuses. Those of the pleura 

 costalis or rather, 4 ntercostalis and of the diaphragm 

 and pleura pulmonalis, are most numerous. They are 

 important in the process of absorption from the pleural 

 and peritoneal cavity respectively. Lymph and lymph 



Fig. 55. Endothelium and Stomata of 

 the Peritonenl Surface of the Septum 

 Cisternae Lymphatics Magnse of the 

 Frog. (Handbook.) 



