286 A MANUAL OF VETERINARY PHYSIOLOGY 



acid staining reveals the fact that fat as such exists in the 

 epithelial cells. It is evident from this that the fats after 

 solution are reconstructed into neutral fats within the epithelial 

 cells. The synthesis of fats in the intestinal epithelium is effected 

 by the same ferment, lipase, which originally split it up ; it is 

 not difficult to imagine a reverse action of lipase in order to bring 

 this about. If an animal be fed on fatty acids without glycerin, 

 neutral fats are found in the thoracic duct. Somewhere, there- 

 fore, the fatty acids have picked up glycerin, and this is 

 believed to be in the intestinal wall, lipase effecting the recon- 

 struction. The story is interesting and instructive ; it em- 

 phasises the specific and selective influence of the living cell, 

 regarding which further evidence will be given later. In the 

 above process the valuable action of the bile-salts in dissolving 

 the fatty acids, and so assisting the lipase of the pancreatic 

 secretion, is very evident. 



When an animal is receiving a known quantity of fat in the 

 food, and the whole of the chyle from the thoracic duct is 

 collected with the object of recovering it, a portion of the fat 

 is found to be missing. In these circumstances only 60 per cent, 

 of the fat can be recovered from the chyle, and that which is 

 missing is believed to be absorbed by the bloodvessels of the 

 villi as fatty acids and soaps, and taken to the liver before its 

 entry into the general blood-stream. This receives further 

 support from the fact that after ligature of the thoracic and 

 right lymphatic duct, 30 to 40 per cent, of fat are absorbed from 

 the intestine. Even after excision of the pancreas> fat absorp- 

 tion is not entirely abolished, and strange to say, more may 

 be found in the intestinal canal than was given by the mouth. 

 This suggests that fat may even be excreted by the intestinal 

 wall. 



All fats are not equally absorbed. In the dog olive oil is 

 taken up more completely (97 per cent.) than any other ; next 

 comes mutton fat, of which 90 to 92 per cent, are absorbed ; 

 while of spermaceti only 15 per cent, are taken up. A dog 

 may absorb up to 21 per cent, of fat in three or four hours, double 

 that in seven hours, and 86 per cent, in eighteen hours. Absorp- 

 tion of fat, in ruminants especially, is a most important question, 

 considering the large sums spent in adding this to the diet of 

 animals intended for food. Experimental inquiry shows that 

 90 per cent, of the fat in linseed cake, 79 per cent, in rape cake, 

 and 88 per cent, in decorticated cotton cake can be absorbed. 

 The digestion of the horse for fat is lower than that of ruminants ; 

 om y 53 P er cent, of the fat in linseed cake can be utilised by 

 this animal. 



The following table shows the power possessed by the herbivora 



