CHAPTEE IX 

 THE LYMPHATIC SYSTEM 



The lymphatic series includes a system of lymphatic channels which 

 collect the lymph from the various tissues of the body and return it 

 to the large veins of the neck, where it mixes with the blood. In the 

 course of this lymph vascular system are various aggregations of lym- 

 phoid or adenoid tissue which occur in the form of lymph nodules or 

 follicles, lymph glands or nodes, and the lymphoid organs. These or- 

 gans are the tonsils, thymus, and spleen. The lymphatic vessels also 

 stand in intimate relation if not in direct communication with the 

 serous and synovial membranes and the bursae. 



LYMPH 



Like the blood, the lymph may be considered as a primary tissue 

 whose intercellular elements are entirely of a fluid nature. In most 

 portions of the body, lymph is a colorless fluid which is scantily provided 

 with corpuscular elements, the lymphatic corpuscles. The lymphatic 

 corpuscles are identical with the leukocytes of the blood. In the lymph 

 most of these cells are of the monoiiuclear form, the small mononuclears 

 or lymphocytes being the most abundant. Lymph also contains a small 

 proportion of polymorphonuclear cells, which not only are derived from 

 the lymphoid tissues, but as wandering cells find their way into the 

 lymphatic vessels from the tissues generally. Blood-platelets are not 

 present in lymph (Howell) ; prothrombin is liberated by the lymphocytes. 



The cells of lymph, predominantly of the small lymphocyte type, are 

 derived from the numerous lymphoid masses (nodes and nodules) 

 through which the lymph passes on its way from the tissues to the sub- 

 da vian veins. According to Davis and Carlson (Amer. Jour. Physiol., 

 vol. 25, 1909) the number of lymphocytes contributed to the blood daily 

 may be more than the total permanently present in the blood. Since the 

 number in a cubic millimeter remains fairly constant, a number must 



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