THE LYMPHATIC SYSTEM. 321 



in small quantity. After coagulation, a separation takes place be- 

 tween the clot and serum, precisely as in the case of blood. 



The movement of the lymph in the lymphatic vessels, from the 

 extremities toward the heart, is accomplished by various forces. 

 The first and most important of these forces is that by which the 

 fluids are originally absorbed by the lymphatic capillaries. Through- 

 out the entire extent of the lymphatic system, an extensive process 

 of endosmosis is incessantly going on, by which the ingredients of 

 the lymph are imbibed from the surrounding tissues, and com- 

 pelled to pass into the lymphatic vessels. The lymphatics are thus 

 filled at their origin ; and, by mere force of accumulation, the fluids 

 are then compelled, as their absorption continues, to discharge 

 themselves into the large veins in which the lymphatic trunks 

 terminate. 



The movement of the fluids through the lymphatic system is 

 also favored by the contraction of the voluntary muscles and the 

 respiratory motions of the chest. For as the lymphatic vessels are 

 provided with valves, arranged like those of the veins, opening 

 toward the heart and shutting backward toward the extremities, 

 the alternate compression and relaxation of the adjacent muscles, 

 and the expansion and collapse of the thoracic parietes, must have 

 the same effect upon the movement of the Lymph as upon that of 

 the venous blood. By these different influences the chyle and 

 lymph are incessantly carried from without inward, and discharged, 

 in a slow but continuous stream, into the returning current of the 

 venous blood. 



The entire quantity of the lymph and chyle has been found, by 

 direct experiment, to be very much larger than was previously 

 anticipated. M. Colin 1 measured the chyle discharged from the 

 thoracic duct of an ox during twenty -four hours, and found it to 

 exceed eighty pounds. In other experiments of the same kind, he 

 obtained still larger quantities. 2 From two experiments on the 

 horse, extending over a period of twelve hours each, he calculates 

 the quantity of chyle and lymph in this animal as from twelve to 

 fifteen thousand grains per hour, or between forty and fifty pounds 

 per day. But in the ruminating animals, according to his observa- 

 tions, the quantity is considerably greater. In an ordinary-sized 

 cow, the smallest quantity obtained in an experiment extending over 



1 Gazette Hebdoinadaire, April 24, 1857, p. 2S5. 



2 Colin, op. cit., vol. ii. p. 100. 



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