80 THE HOESE IN HEALTH AND DISEASE 



the stomach quickly. When the stomach is well filled the con- 

 tents are only penetrated very superficially by the water. 



(C) Digestion in the Small Intestine. — During the process of 

 stomach digestion that portion of the ingesta which has been acted 

 upon by the gastric juice is gradually passed on as chyme into the 

 small intestine. 



Chyme is a watery solution of the products of gastric digestion 

 with a large quantity of undissolved matter in suspension. It is 

 soup-like in consistency, and contains most of the fibrous parts of 

 the diet, particularly cellulose. Shortly after reaching the small 

 intestine the chyme becomes neutralized, and then assumes an 

 alkaline reaction from having been mixed with the biliary, pan- 

 creatic, and intestinal secretions. These alkaline digestive juices 

 cause the acid albumin to precipitate, which changes the appear- 

 ance of the chyme to a yellowish, frothy fluid, with clot-like par- 

 ticles held in suspension. 



Bile is secreted by the liver, from which it is conveyed to the 

 small intestine by the bile-duct. As the horse has no gall-bladder, 

 the flow of bile is continuous, but is much freer when intestinal 

 digestion is going on than in a fasting animal. 



A physical examination of bile shows that it is a watery fluid, 

 alkaline in reaction, and very bitter to the taste. It is yellowish- 

 green in color when fresh, and has an average specific gravity of 

 1005. According to Colin, from 250 to 310 c.c. of bile are secreted 

 per hour. The principal constituents of the bile are water (about 

 92 per cent.) the salts of the bile acids, biliary pigments, fats, soaps, 

 sometimes a little protein and inorganic salts, and certain waste 

 products like lecithin and cholesterol. 



The salts of the bile acids are present as sodium glycocholate 

 and taurocholate. The former is found in larger quantities in her- 

 bivora. The bile-pigments are bihrubin and biliverdin. The first 

 is apparently derived from the blood-pigment. Bihverdin is pro- 

 duced from bilirubin by oxidation, and gives the bile its character- 

 istic color. 



Bile acts chiefly as a solvent and emulsifier of fats. It is most 

 active in the presence of pancreatic juice. It does not act on 

 proteins or carbohydrates ; in fact, intestinal digestion can proceed 

 without the presence of bile. 



Pancreatic juice reaches the intestine by two separate and dis- 

 tinct ducts, as already described. The secretion is indirectly stimu- 



