262 PHYSIOLOGICAL PHYSICS. [Chap. xxn. 



the stomach and intestines there are two different 

 liquids, the chyme or chyle on the one hand, the 

 blood circulating through the intestinal capillaries on 

 the other. These two are separated by a thin 

 organic membrane consisting of the epithelium of the 

 inner surface of the intestinal canal, the thin walls of 

 the capillaries, and the small amount of adenoid 

 tissue between the two. These are the conditions of 

 osmosis. Observe, again, that the blood is an al- 

 buminous fluid, and that albumen is one of the most 

 sparingly diffusible of substances, requiring a very 

 large quantity of water to pass through the membrane 

 to its side before even a small portion of it passes 

 through to the other side. On the other hand, the 

 substances in solution in the chyme or chyle are 

 diffusible. Herein, also, lies the rationale of the 

 action of the various digestive fluids. Their action 

 is on starch, albumen, and fat, non-diffusible and 

 non-dialysable substances. Starch is converted into 

 sugar, and albumen into peptone, both capable of 

 diffusion and dialysis. It is hardly within the province 

 of this work to discuss the other elements in connection 

 with the absorption of fat. By the action of the diges- 

 tive fluids, therefore, the obstacles to osmosis, so far as 

 the fluid food stuffs are concerned, are got rid of. Not 

 only, therefore, are the conditions of osmosis present so 

 far as the animal membrane separating two different 

 liquids is concerned, but, owing to the character of 

 the liquids, the direction of the osmosis is readily 

 determined. 



A remarkably interesting fact bearing upon the 

 absorption from the stomach is to be noted. Graham 

 showed by experiments that a small quantity of 

 dilute hydrochloric acid present in an osmometer 

 interfered greatly with the passage of the endosmotic 

 current. Thus the feeble acidity of the contents of 

 the stomach, acting in this way, will greatly interfere 



