VARIATIONS AND FUNCTIONS OF BILE. 193 



large intestine as it is in the small. But even this inconsiderable 

 quantity, found in contents of the large intestine, does not con- 

 sist of biliary matters ; for the watery solutions being treated with 

 sugar and sulphuric acid, those from both the upper and lower 

 portions of the small intestine always gave Pettenkofer's reaction 

 promptly and perfectly in less than a minute and a half; while in 

 that from the large intestine no red or purple color was produced, 

 even at the end of three hours. 



The small intestine consequently contains, at all times, substances 

 giving all the reactions of the biliary ingredients; while in the 

 contents of the large intestine no such substances can be recognized 

 by Pettenkofer's test. 



The biliary matters, therefore, disappear in their passage through 

 the intestine. 



In endeavoring to ascertain what is the precise function of the bile 

 in the intestine, our first object must be to determine what part, if( 

 any, it takes in the digestive process. As the liver is situated, like 

 the salivary glands and the pancreas, in the immediate vicinity of 

 the alimentary canal, and like them, discharges its secretion into 

 the cavity of the intestine, it seems at first natural to regard the 

 bile as one of the digestive fluids. We have previously shown, 

 however, that the digestion of all the different elements of the food 

 is provided fcr by other secretions ; and furthermore, if we examine 

 experimentally the digestive power of bile on alimentary substances, 

 we obtain only a negative result. Bile exerts no special action upon 

 either albuminoid, starchy, or oleaginous matters, when mixed with 

 them in test-tubes and kept at the temperature of 100 F. It has 

 therefore, apparently, no direct influence in the digestion of these 

 substances. 



It is a very remarkable fact, in this connection, that the bile pre- 

 cipitates by contact with the gastric juice. If four drops of dog's bile 

 be added to 3j of gastric juice from the same animal, a copious 

 yellowish- white precipitate falls down, which contains the whole of 

 the coloring matter of the bile which has been added ; and if the 

 mixture be then filtered, the filtered fluid passes through quite 

 colorless. The gastric juice, however, still retains its acid reaction. 

 This precipitation depends upon the presence of the biliary sub- 

 stances proper, viz., the glyko-cholate and tauro-cholate of soda, and 

 lQt upon that of the incidental ingredients of the bile. For if the 

 bile be evaporated to dryness and the biliary substances extracted 

 13 



