LYMPHATIC SYSTEM. 



189 



nite walls. These vessels, which are lined with characteristic 

 endothelium, form a more or less dense network of lymphatic 

 capillaries, from which spring the tributaries of the lymph ves- 

 sels. (Figs. 82 and 83.) 



The lymphatic vessels are throughout slender thin-walled chan- 

 nels with close-set valves, usually in pairs, and with frequent 

 anastomoses. They lie imbedded in the connective tissue, and 



FIG. 82. 



Lymph Channels from the thoracic side of the central tendon of the 

 diaphragm of the rabbit, treated with silver nitrate. The fine lines indicate 

 the boundaries of the endothelium cells lining the lymph channels. The 

 dark part shows the islets between the lymphatic network. (Klein.) 



when empty are difficult to see, owing to their extreme delicacy. 

 They converge towards a central vessel called the thoracic duct, 

 which, passing from the abdominal cavity, through the thorax, 

 reaches the left side of the neck, and opens into the angle of 

 junction of the two great veins from the head and upper ex- 



