188 A Manual of Veterinary Physiology. 



connection with this portion of intestine become opaque, 

 though previously they were tilled with a colourless fluid. 

 As the chyme passes along the bowel the other lacteals in 

 their turn become opaque, until at last the whole of them 

 are tilled with this milky fluid. Colin draws especial 

 attention to this regular invasion of the lacteals from the 

 duodenum to the ileum. 



The various principles of the food having been rendered 

 fit to be taken up into the system, by what channels is this 

 accomplished ? 



Absorption of Fat. — Experimental inquiry, limited almost 

 entirely to dogs, points to the lacteals as the means by which 

 the fatty part of the food is taken up. It has been observed 

 that these vessels after a diet rich in fat are filled with a 

 milky fluid rich in the same substance, whilst the blood in 

 the portal vein does not contain more fat than that of any 

 other vein in the body. Clearly, therefore, in dogs at least, 

 the lacteals take up the fat. But what about herbivora, 

 the diet of which contains but little fat, that of the horse in 

 particular? Exactly the same appearance of milky lacteals 

 is obtained in the horse after feeding on a diet notoriously 

 deficient in fat ; it is possible, therefore, that in the horse 

 the lacteals may take up other substances than fat, and that 

 the milky appearance is not due to fat alone. The absorp- 

 tion of fats is not perfect, for even in dogs only about 

 60 per cent, of the fat eaten can be recovered from the 

 thoracic duct, and none, as we have mentioned before, enters 

 the blood. 



Colin expressly states that proteids and sugar are also 

 absorbed by the lacteals in the horse, and on this point 1 am 

 certainly inclined to agree with him, in spite of experiments 

 to the contrary on dogs. This observer injected glucose 

 into the intestine, and the chyle contained in a short time 

 a decided increase in sugar. 



Returning to the question of fat absorption, we obsorve 

 that by the action of the epithelium covering the villi the 

 minute fat globules forming the emulsion arc drawn in and 

 passed on to the lacteals . from here they ascend the 



