68 PHYSIOLOGY AT THE FARM. 



is continuous with a layer of organic muscular fibres situated 

 within the mucous membrane of the intestine. No nervous 

 twigs have been found within the villi. Each villus, being a 

 process of the mucous membrane, has an investing basement 

 membrane, the outer surface of which is covered with a layer 

 of cylindrical epithelium. 



Duodenal Digestion. The chyme, or partially changed mass 

 which passes by the pyloric orifice from the stomach into the 

 duodenum or highest part of the small intestines, is destined to 

 undergo important changes before it is fit to afford the chyle 

 to the intestinal villi. The bile, the pancreatic juice, and the 

 peculiar secretion of the glands of the duodenal mucous mem- 

 brane, are the agents by which such changes are to be effected. 

 It was formerly believed that nothing derived from the food 

 capable of nourishing the living frame, found its way into the 

 blood by any other channel than the lacteal vessels. It is 

 now, however, held to be well established, that the blood-ves- 

 sels, and, in particular, the capillary network of blood-vessels, 

 freely absorb fluid or gaseous bodies, or even solid matter 

 soluble in the blood, when brought into contact with their 

 walls. Hence it follows that all such bodies contained in the 

 food, or formed during the processes of gastric or duodenal 

 digestion, as are soluble in the blood, may be freely absorbed 

 into the blood independently of the lacteal absorption. Even 

 oil, when minutely divided, as in emulsion, will pass slowly 

 into the blood-vessels. The process termed endosmosis before 

 referred to (p. 47) has a large share in such absorption, and 

 hence it is observed that the amount of absorption in this 

 manner is great in proportion as the fluid is of small density. 



Absorption of Nutriment. Though the subject of the ab- 

 sorption of certain soluble substances by the capillary blood- 

 vessels of the mucous membrane of the stomach and small 

 intestines, during the progress of digestion, be as yet far from 



