CHAPTER XXIX 

 LYMPH 



BY means of the circulatory system the blood is taken to the great 

 network of capillaries which ramify in their myriads amid the various 

 tissues of the body. Since, however, this blood capillary system is. 

 a closed one, blood itself does not come into actual contact with the 

 tissue cells themselves.* These cells are bathed in a fluid the tissue 

 fluid, or lymph and it is this fluid which finally takes to the tissues 

 the substances necessary for their proper nutrition and adequate 

 working, and takes from them the products of their activity. 



The lymphatic system is a most extensive one. It consists of the 

 interstitial or lacunar spaces which exist in almost all parts of the 

 body ; the delicate lymphatic capillaries ; the larger lymphatic vessels, 

 which ultimately unite to form the thoracic duct or the right lymphatic 

 duct ; the lymphatic tissues of the body, such as the lymphatic glands ; 

 and the lymphatic tissue incorporated in the spleen, thymus, etc. 

 The large serous spaces, such as the peritoneum, pericardium, may 

 also be included in this system. 



For many years past the exact relationship between the inter- 

 stitial spaces and the lymphatic vessels has been the subject of con- 

 siderable discussion. One view, formerty accorded almost general 

 acceptation, is that the interstitial spaces, or lacunae, communicate 

 directly with the delicate lymph capillaries, which in turn unite to 

 form larger channels or lymphatics, and ultimately open into the 

 venous system by the thoracic duct or the right lymphatic duct. 



According to this view, the tissue fluids bathing the cells and 

 the lymph flowing from a lymphatic duct are one and the same fluid, 

 since there is absolute continuity between the duct lumen and the 

 tissue spaces. Another view, which has recently gained much support, 

 is that the interstitial tissue spaces do not directly communicate with 

 the lymph capillaries. The lymphatic system, according to this view, 

 is, as regards the tissue spaces, a closed system. It probably communi- 

 cates by stomata with large serous spaces, such as the peritoneal 

 space, and possibly also with the spaces of certain mucosae e.g., the 

 bronchial and nasal. 



On this hypothesis-!, the tissue fluid of the interstitial spaces is dis- 

 tinct from the lymph of the lymphatic system. Little or' no thing is 

 known as to the exact composition of such tissue fluid ; it is assumed 

 to be of much the same composition as the lymph. This bathes the 



* Except in the spleen and liver. Blood-capillaries, too, run into the giant 

 ganglion cells which feed the electric organ in Malapterurus. 



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