THE LYMPHATIC SYSTEM. 333 



system is present in the cat, it is much less easily demonstrated 

 than the superficial system. 



4. Lymphatics of the Thorax and Abdomen. In the 

 thorax are a number of lymphatic glands which are apparently 

 not constant in number and position. One is commonly found 

 dorsad of the bifurcation of the superior vena cava, one ventrad 

 of the mammary vein, several small ones about the bifurcation 

 of the trachea, one or more in the region of the aortic arch, 

 and a number of small ones scattered in the mediastinum. 

 The vessels from these glands finally join either the right lym- 

 phatic duct or the thoracic duct; the details have not been 

 worked out and are probably variable. 



In the abdominal cavity a number of mesenteric glands, of 

 considerable size, are found in the mesentery and in the meso- 

 colon. In the mesocolon these are usually separate, forming 

 a chain of glands following the colon about one and a half 

 centimeters from it. In the mesentery the glands are mostly 

 united into a very large one, formerly known as the pancreas 

 aselli ; this is the largest lymph-gland in the body. It is a 

 curved structure, four or five centimeters in length, lying in 

 the central region of the mesentery. 



Into the mesenteric glands pass lymphatic vessels from the 

 viscera of the abdomen. From the mesenteric glands one or 

 two large lymphatic vessels pass craniodorsad, at first with the 

 portal vein, then dorsad of it. This vessel reaches the dorsal 

 side of the aorta near the cranial end of the kidney, where it 

 enters a large fusiform vessel, the receptaculum chyli, which 

 stretches from the cranial end of the kidney craniad between 

 the crura of the diaphragm into the thorax. The receptaculum 

 receives other lymphatics from the various organs of the 

 abdominal cavity as well as vessels coming from the pelvic 

 region, and from the iliac glands. These lie beside the iliac 

 artery, receive lymphatics from the hind limbs, and send lym- 

 phatics craniad to the receptaculum chyli. The latter forms 

 the beginning of the thoracic duct. 



The thoracic duct (Fig. 118, 5, page 282) enters the 

 thoracic cavity between the crura of the diaphragm as a con- 

 tinuation of the receptaculum chyli. It lies on the dorsal side 



