CHAPTER X. 



THE LYMPH VASCULAR SYSTEM. 



The lymphatics are in all particulars like the blood 

 vessels in structure, .except that even the largest 

 lympatics have only a small amount of muscle tissue. 

 In all the tissues and organs there are small spaces that 

 are called pericellular spaces. These spaces are the 

 beginning of lymphatic vessels. The small vessels 

 continue to join until they reach the thoraic duct, which 

 pours its contents into the sub-clavian vein : at this 

 point the inner court of the duct is folded over on it- 

 self and forms a valve to prevent blood from flowing 

 into the duct. All along the course of the vessels are 

 found similar valves, which prevent the lymph from 

 flowing but one way. While all the tissues of the body- 

 are rich in lymph vessels, the ones supplied most are 

 the white fibrous, areola, blood vessels and nerves. In 

 the last two locations they are called perivascular and 

 perineurial lymphatics, respectively. The lymph is a 

 clear fluid, having floating in it a large number of 

 cells and fat granules. The cells are very much like 

 5 (65) 



