Section 2. 



Chyle. 



In the thoracic duct the lymph from the body meets with the 

 lymph coming from the intestines, termed ' chyle.' This chyle 

 is derived from the villi, and passes up the mesentery by many 

 vessels, which in the horse are said by Colin to number 1,200. 

 Each of these passes through a lymphatic gland before entering 

 the receptaculum chyli. Chyle is closely allied to lymph in its 

 chemical composition, but it differs from it in containing, during 

 digestion, a quantity of neutral fat, which gives it a milky appear- 

 ance. The amount of this fat in dogs may vary from 2 per cent. 



to 15 per cent., or even more. The 

 fat is partly in the condition of 

 measurably large droplets, such as 

 are seen in milk, but the bulk of 

 it exists as extraordinarily minute 

 particles ; hence the name ' mole- 

 cular basis/ which is applied to 

 the fat particles in chyle collec- 

 tively. 



The Villi. — We have mentioned 

 that in the ordinary tissues the 

 radicles of the lymph vessels are 

 the lymph spaces, but in the wall 

 of the small intestines the origins 

 of the lymph vessels are highly 

 differentiated structures, known as 

 villi and solitary glands. The villi 

 (Fig. 85) are innumerable projec- 

 tions from the inner surface of 

 the mucous membrane shaped like 

 minute fingers ; they are only found 

 in the small intestines, and have 

 been calculated by Colin to amount to forty or fifty millions in 

 the horse and ox. In the interior and central part of the villus is 

 a vessel termed the lacteal ; it may be single or multiple, straight 

 or branched, and at the base of the villus it opens by a valvular 

 arrangement into the lymphatic system. Surrounding the lacteal 

 is a network of capillary bloodvessels, while filling up the finger 

 of the villus, not otherwise occupied by vessels, is a peculiar 

 structure found especially in lymphatic glands, and known as 



278 



a <- c 



Fig. 85. — Vertical Section of a 

 Villus : Cat. X 300 (Stewart). 



a, Layer of columnar epithelium 

 covering the villus — the outer 

 edge of the cells is striated ; 

 b, central lacteal of villus ; c, 

 unstriped muscular fibres ; d, 

 mucin forming goblet cells. 



