CHAPTER X. 

 ABSORPTION. 



Absorption is the process by which nutritive material is trans- 

 ferred from the tissues, from the serous cavities, and from the mucous 

 surfaces of the body, intp the blood. The most important of these 

 surfaces, especially in its relation to the formation of blood, is the 

 mucous surface of the alimentary canal, for it is from this organ that 

 the new materials are derived which maintain the quantity and 

 quality of the blood. The absorption of material from the inter- 

 stices of the tissues and from the serous cavities may be regarded as 

 an act of resorption, or a return to the blood of liquid nutritive material 

 which has escaped through the walls of the capillary blood-vessels 

 for purposes of nutrition, and which, if not returned, would lead to 

 an accumulation and the development of edematous conditions. 



The anatomic mechanisms involved in the absorptive process 

 are, primarily, the tissue or lymph-spaces, the lymph- and blood- 

 capillaries; secondarily, the lymph-vessels and the veins. 



Tissue or Lymph-spaces; Lymph-capillaries. Everywhere 

 throughout the body, in the connective-tissue system and in the inter- 

 stices of the several structures of which an organ is composed, are 

 found spaces or clefts of irregular shape and size, determined largely 

 by the structure of the organ in which they are found, which have 

 been termed tissue or lymph-spaces, from the fact that they contain 

 a clear fluid, lymph. These spaces are devoid for the most part of 

 any endothelial lining, but as they communicate more or less freely 

 one with another, there is a circulation of lymph through them and 

 around the islets of tissue (Fig. 87). In addition to the connective- 

 tissue lymph-spaces, different observers have described special spaces 

 or clefts in organs such as the kidney, liver, spleen, testicle, and in 

 all secreting glands between their basement membrane and the sur- 

 rounding blood-vessels, all of which contain a greater or less quan- 

 tity of lymph. |\ Within the brain, spinal cord, bone, and other tissues 

 it has been shown that the smallest blood-vessels and capillaries are 

 bounded and limited by a cylindrical sheath containing lymph, which 

 is known as a peri vascular lymph-space 1 A similar sheath surrounds / r 

 the smallest nerve-bundles and fibers, enclosing a perineural lymph- ~Vp, 

 space. I The large serous cavities of the body, pleural, peritoneal, 

 pericaraial, etc., are also to be regarded as lymph-spaces. The sur- 

 faces of these cavities, however, are covered with a layer of endo- 



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