l82 ORGANIC AGRICULTURAL CHEMISTRY 



action appears to rest in constituents of the bile known as bile 

 salts. These salts are usually sodium salts of two acids, glyco- 

 cholic and taur acholic acids, which are so-called conjugated acids 

 of glycocoll or glycine and cholic acid in the case of glycocholic 

 acid, and taurine and cholic acid in taurocholic acid. Cholic 

 acid itself is a complex acid probably monobasic, but of un- 

 determined constitution. 

 l" The second way in which the bile assists in the digestion of 

 fats is in the formation of soaps and emulsions. Bile is alkaline 

 in reaction and the alkalies present unite with the free fatty 

 acids formed by the hydrolysis of the fats, and the result is soap. 

 These soaps or alkali salts of the fatty acids are probably 

 directly absorbed through the cell membranes. The emulsify- 

 ing power of bile may be due in part to the formation of these 

 soaps, but it is also a function of the bile itself. When bile 

 alone is mixed with pure fat, the fat is emulsified and can then 

 diffuse through cell membranes. In these two ways, then, by a 

 stimulation of the lipolytic enzyme of pancreatic juice, and by 

 the formation of soaps and emulsions, the bile assists in the 

 pancreatic digestion and absorption of fats. 



The secretion of bile and its flow into the intestine is de- 

 pendent upon the presence in the intestine of undigested fat 

 food and probably also of protein food, and it seems to be regu- 

 lated by the same or similar hormones as were described in 

 connection with the flow of pancreatic juice. 



Bile is a viscous alkaline liquid of specific gravity, i.oi to 

 1.04. It is of various colors, mostly yellow, green or brown, 

 and has a bitter taste. The amount secreted daily varies 

 between 500 and iioo c.c. per day for man. 



The Large Intestine 



It was previously stated that, in man, no digestion occurs in 

 the large intestine. This is true so far as new digestive pro- 

 cesses or the secretion of juices containing digestive enzymes 

 are concerned. No digestive juices containing enzymes are 

 secreted in the large intestine. A continuation of digestive 



