296 HAND-BOOK OF PHYSIOLOGY. 



Demonstration of Lymphatics of Diaphragm. The stomata on the 

 peritoneal surface of the diaphragm are the openings of short vertical 

 canals which lead up into the lymphatics, and are lined by cells like those 

 of germinating endothelium (p. 23). By introducing a solution of Berlin 

 blue into the peritoneal cavity of an animal shortly after death, and sus- 

 pending it, head downward, an injection of the lymphatic vessels of the 

 diaphragm, through the stomata on its peritoneal surface, may readily be 

 obtained, if artificial respiration be carried on for about half an hour. In 

 this way it has been found that in the rabbit the lymphatics are arranged 

 between the tendon bundles of the centrum tendineum; and they are 

 hence termed interfascicular. The centrum tendineum is coated by 

 endothelium on its pleural and peritoneal surfaces, and its substance con- 

 sists of tendon bundles arranged in concentric rings toward the pleural 

 side and in radiating bundles toward the peritoneal side. 



FIG. 21 1 .Peritoneal surface of septum cisternae lymphaticee magnee of frog. The stomata, some 

 of which are open, some collapsed, are surrounded by germinating endothelium. x 160. (Klein.) 



The lymphatics of the anterior half of the diaphragm open into those 

 of the anterior mediastinum, while those of the posterior half pass into a 

 lymphatic vessel in the posterior mediastinum, which soon enters the tho- 

 racic duct. Both these sets of vessels, and the glands into which they 

 pass, are readily injected by the method above described; and there can 

 be little doubt that during life the flow of lymph along these channels is 

 chiefly caused by the action of the diaphragm during respiration. As 

 it descends in inspiration, the spaces between the radiating tendon bun- 

 dles dilate, and lymph is sucked from the peritoneal cavity, through the 

 widely open stomata, into the interfascicular lymphatics. .During expira- 

 tion, the spaces between the concentric tendon bundles dilate, and the 

 lymph is squeezed into the lymphatics toward the pleural surface. (Klein. ) 

 It thus appears probable that during health there is a continued sucking 

 in of lymph from the .peritoneum into the lymphatics by the "pumping" 

 action of the diaphragm; and there is doubtless an equally continuous 

 exudation of fluid from the general serous surface of the peritoneum. 

 When this balance of transudation and absorption is disturbed, either by 

 increased transudation or some impediment to absorption, an accumula- 

 tion of fluid necessarily takes place (ascites). 



Stomata have been found in the pleura; and as they may be presumed 

 to exist in other serous membranes, it would seem as if the serous cavities, 



