LYMPHATICS 



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subclavian vein 

 Thoracic duct 



Lymph node of 

 lacteal system 



stantly drained away by delicately walled tubes, the 

 lymphatics, whose expanded mouths open into them. 

 The lymphatics join together to form larger lymph 

 canals, very much as the capillaries unite to form the 

 veins. The flow of lymph through the lymphatics is 

 brought about by the exter- 

 nal pressure due to the ac- 

 tivity of the muscles and 

 other tissues lying near 

 them. 



The two large lymphatic 

 ducts which result from the 

 union of all the smaller 

 branches, pass respectively 

 into the two large veins 

 under the collar bone on 

 the sides of the neck, 

 through openings pro- 

 tected by valves, so that 

 the blood cannot pass back 

 through the lymphatics. 

 Of these ducts, the left is 

 much the larger and carries, in addition to the lymph, 

 the lacteal flow from the intestinal tract. The total 

 amount discharged from the lymphatics into the veins is 

 estimated to be more than two quarts in every twenty- 

 four hours. 



Function of lymphatic system The function of 

 the lymphatic system is twofold. It brings the plasma 

 of the blood containing the dissolved food materials 

 into closer contact with the cells than is possible when 

 the plasma is within the capillaries. By means of the 

 lymph, the tissue cells are bathed in a constant and fresh 

 stream of food-containing fluid, from which they can 



FIG. 90. Lacteals and thoracic duct. 



