ABSORPTION. 



301 



ings or STOMATA exist, by which lymphatic capillaries directly communi- 

 cate with parts hitherto supposed to be closed cavities. 



When absorption into the lymphatic system takes place in membranes 

 covered by epithelium or endothelium through the interstitial or inter- 

 cellular cement-substance, it is said to take place through pseudostomata, 

 already alluded to. 



FIG. 216. Lymphatic vessels of the head and neck and the upper part of the trunk (Mascagni). 

 1/6. The chest and pericardium have been opened on the left side, and the left mamma detached 

 and thrown outwards over the left arm, so as to expose a great part of its deep surface. The prin- 

 cipal lymphatic vessels and glands are shown on the side of the head and race, and in the neck 

 axilla, and mediastinum. Between the left internal jugular vein and the common carotid artery, 

 the upper ascending part of the thoracic duct marked 1, and above this, and descending to 2, the 

 arch and last part of the duct. The termination of the upper lymphatics of the diaphragm in the 

 mediastmal glands, as well as the cardiac and the deep mammary lymphatics, is also shown. 



Demonstration of Lymphatics of Diaphragm. The stomuta on the 

 peritoneal surf ace, of the diaphragm are the openings of short vertical 

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

 of germinating endothelium. By introducing a solution of Berlin blue 

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

 ing it, head downwards, an injection of the lymphatic vessels of the 

 diaphragm, through the stomata oh 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 ar- 

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

 are hence termed interfascicular. The centrum tendineum is coated by 



