ABSORPTION. 115 



lead to an accumulation of such fluid and the development of drop- 

 sical conditions. 



The anatomic mechanisms involved in the absorptive processes are, 

 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 bun- 

 dles 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 lacuna, 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 addi- 

 tion to the connective-tissue lymph-spaces, various observers have 

 described special lymph-spaces in the testicle, kidney, liver, thymus 

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

 membrane and blood-vessels ; around blood-vessels (perivascular 

 spaces), and around nerves. The serous cavities of the body peri- 

 toneal, pleural, pericardial, etc. may also be regarded as lymph- 

 spaces, which are in direct communication by open mouths or 

 stomata with the lymph capillaries. This method of communica- 

 tion 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 irregu- 

 lar shape. In most situations they are intimately interwoven with 

 the blood-vessels, from which, however, they can be readily dis- 

 tinguished by their larger caliber and irregular expansions. The 

 wall of the lymph-capillary is formed by a single layer of epithelioid 

 cells, with sinuous outlines, and which accurately dovetail 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 villus enters 

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

 regurgitation. The lymph capillaries anastomose freely with one 

 another, and communicate on the one hand with the lymph-spaces, 

 and on the other with the lymphatic vessels proper, 



