CHAPTER XV. 



THE LYMPH. 



IN its course through the blood-capillaries a portion of the plasma 

 passes out through the vessel-walls and enters a system of irregular 

 interfascicular clefts, which are bounded by bundles of fibrous tissue 

 and constitute the radicles of the lymphatic system. Through these 

 clefts the plasma reaches the individual cells of the various tissues 

 and organs of the body, and supplies these with the requisite 

 nourishment, while at the same time it takes up the waste matter 

 that is formed in the metabolism of the cells, and through the 

 lymph-vessels carries these into the venous current of the blood. 

 This fluid, which thus contains the various constituents of the 

 blood-plasma and the decomposition-products of the cells, is termed 

 the lymph. 



In addition to the lymph-vessels proper and their radicles, the 

 lymph-clefts, this fluid is also found in the so-called serous cavities 

 of the body, viz., the pleura, the peritoneal and pericardial cavities, 

 in the ventricles of the brain and the spinal cord, in the communi- 

 cating subarachnoid space, and also in the anterior chamber of the 

 eye. In health, however, these cavities contain but little fluid, and 

 quantities sufficient for analytical purposes can normally be obtained 

 only from the pericardial sac, and at times from the subarachnoid 

 space. Under pathological conditions, however, large accumulations 

 of fluid may be observed, and not only in the serous cavities of the 

 body, but also in the areolar connective tissue, beneath the skin, 

 and beneath the muscles. When due to circulatory disturbances, a 

 hydrsemic condition of the blood, or an insufficient elimination of 

 water through the kidneys, such accumulations of fluid are spoken 

 of as transudates, while the term exudates is applied to similar 

 accumulations of inflammatory origin. 



Formerly it was supposed that the lymph resulted from the blood- 

 plasma through a simple process of filtration or transudation only, 

 and in accordance with this view we find that in the various accumu- 

 tions of lymph the salts and extractives are present in about the 

 same amount as in the blood-plasma. Heidenhain, however, has 

 shown that the flow of the lymph-current is far too sluggish to 

 supply the various organs of the body with the proper amount of 

 nourishment, supposing its composition to bo everywhere the same 

 as that of the blood-plasma. We are hence forced to the conclusion 

 that the endothelial cells of the capillaries possess a selective secre- 

 tory power similar to that of the renal epithelium, and are thus 



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