72 PHYSIOLOGY AT THE FARM. 



or chemical, on this principle. It is agreed, then, that the 

 digestion of oil commences in the duodenum. There the oil 

 ceases to appear in large drops or in semi-fluid masses, and 

 takes on the form of minute drops. The farther it descends 

 in the small intestine so much the more minute do these drops 

 become, so that at length the oil becomes finely comminuted, 

 and the chyme presents an emulsive appearance. Since the 

 lacteals are seen to be distended with white oily chyle after 

 the use of oily food, it cannot be doubted that the principal 

 channel by which the oil makes its way into the blood is by 

 lacteal absorbent vessels in the intestinal walls. It has been 

 taught that there are special cells in each of the villi solely 

 charged with the absorption of oil ; and while it is certain that 

 oil makes its way to the blood chiefly by the lacteal absorbents, 

 it is undeniable that the capillary blood-vessels of the intestinal 

 mucous membrane also take up oil, though in less considerable 

 quantities. This latter fact is confirmed by the manifest aug- 

 mentation of oil in the portal blood of animals a few hours 

 after they have been fed a fact which cannot be explained 

 by the assumption of a conversion of carbo-hydrates into oil 

 during their passage from the intestinal cavity into the portal 

 vein. It is, however, maintained on high authority that there 

 is a direct transmission of oil into the blood of the capillaries 

 from the epithelial cells and the parenchyma of the villi. 



Proteine Compounds. The course of the subject of diges- 

 tion leads now to the azotised proximate principles or plastic 

 principles. These are the albuminoid group, called also of 

 late the ^proteine principles, namely, albumen, caseine, fibrine. 

 The name peptones has been applied by some authorities to 

 albumen, fibrine, and caseine, after the metamorphosis which 

 they undergo in the stomach under the influence of the gastric 

 juice. These peptones then, it is conceived, undergo absorp- 

 tion, and are in the lacteal system reconverted into the well- 



