ABSORPTION. 103 



primarily, the lymph-spaces, the lymph-capillaries, and the blood-capillaries; 

 secondarily, the lymphatic vessels and larger blood-vessels. 



Lymph-spaces, Lymph-capillaries, Blood-capillaries. Everywhere 

 throughout the body, in the intervals between connective-tissue bundles and 

 in the interstices of the several structures of which an organ is composed, are 

 found spaces of irregular shape and size, determined largely by the nature of 

 the organ in which they are found, which have been termed lymph-spaces or 

 lacunas, from the fact that during the living condition they are continually 

 receiving the lymph which has escaped from the blood-vessels throughout 

 the body. In addition to the connective-tissue lymph-spaces, various ob- 

 servers have described special lymph-spaces in the testicle, kidney, liver, thy- 

 mus gland, and spleen; in all secreting glands between the basement membrane 

 and blood-vessels; around blood-vessels (peri vascular spaces), and around 

 nerves. The serous cavities of the body peritoneal, pleural, pericardial, 

 etc. may also be regarded as lymph-spaces, which are in direct communi- 

 cation by open mouths or stomata with the lymph capillaries. This method 

 of communication is not only true of serous membranes, but to some extent 

 also of mucous membranes. The cylindric sheaths and endothelial cells 

 surrounding the brain, spinal cord, and nerves can also be looked upon as 

 lymph-spaces in connection with lymph-capillaries. 



The lymph-capillaries, in which the lymph- vessels proper take their origin, 

 are arranged in the form of plexuses of quite irregular shape. In most 

 situations they are intimately interwoven with the blood-vessels, from which, 

 however, they can be readily distinguished by their larger caliber and irreg- 

 ular expansions. The wall of the lymph- capillary is formed by a single 

 layer of epithelioid cells, with sinuous outlines, and which accurately dove- 

 tail with one another. In no instance are valves found. In the villus of the 

 small intestine the beginning of the lymphatic is to be regarded as a lymph- 

 capillary, generally club-shaped, which at the base of the vijlus enters a 

 true lymphatic; at this point a valve is situated, which prevents regurgitation. 

 The lymph capillaries anastomose freely with one another, and communic- 

 cate on the one hand with the lymph-spaces, and on the other with the lym- 

 phatic vessels proper. 



As the shape, size, etc., of both lymph-spaces and capillaries are deter- 

 mined largely by the nature of the tissues in which they are contained, it is 

 not 'always possible to separate the one from the other. Their function, 

 however, may be regarded as similar viz., the collection of the lymph which 

 has escaped from the blood-vessels, and its transmission onward into the 

 regular lymphatic vessels. 



The blood-capillaries not only permit the escape of the liquid nutritive 



