324 ACTION OF THE BILE. 



ACTION OF THE BILE. 



The bile is a metabolic product largely destined for excretion, and 

 participating in but small measure in the digestive process. 



Bile plays an important part in the absorption of fat. It forms a 

 fine emulsion of the neutral fats, in consequence of which the fatty 

 granules, in addition to chemical division, are especially rendered capa- 

 ble of passing through the cylindrical epithelium of the small intes- 

 tine. It does not effect the chemical decomposition of the neutral fats 

 into glycerin and fatty acids, as does the pancreatic juice, but it is capable 

 of dissolving the fatty acids through the salts of the biliary acids. 



The soaps present in the intestine are soluble in the bile and are capable 



in turn of greatly increasing the emulsifying power of the bile. The bile itself, 



however, is capable of converting the fatty acids directly into an acid solution 

 that exerts an active emulsifying influence. 



As the bile, like a soap solution, bears a certain relation to aqueous 

 fluids as well as to fats, it may conduce to diffusion between the two, as 

 the membrane can be moistened and can imbibe both fluids. 



From the foregoing it follows that the bile is of great importance for the 

 preparation and absorption of fats. This can also be demonstrated by experi- 

 ments on animals, in which the bile is entirely conveyed externally through 

 a fistula. Dogs thus treated absorb, at the most, 40 per cent, of the fat ingested, 

 while normal dogs absorb 99 per cent. The chyle of such animals is, accord- 

 ingly, deficient in fat, and is not white, but transparent. The feces, however, 

 contain more fat and are greasy. The animals eat greedily; the tissues of the 

 body show great deficiency of fat, even when the nutrition in general has not 

 suffered much. In human beings suffering from derangement in the secretion 

 of bile, a diet rich in fat is, for this reason, contraindicated. 



Fresh bile contains some diastatic ferment, as starch and glycogen 

 are converted into sugar. 



This ferment is, however, absorbed from the walls of the alimentary canal 

 and is then excreted as ptyalin by the bile, as by the urine also. 



The bile acts as a stimulant to the intestinal musculature and 

 thus contributes to absorption in general. 



Perhaps through its biliary acids, acting as irritants, it causes the muscles 

 of the intestinal villi to contract from time to time, in consequence of which 

 these propel the contents of their lymph-spaces into the larger lymph-trunks, 

 and thus are capable of absorbing renewed amounts. 



Also the musculature of the intestinal wall itself appears to undergo excita- 

 tion, probably through the agency of the myenteric plexus. In favor of this 

 view is the fact that intestinal peristalsis is greatly impaired in animals with biliary 

 fistulas and in the presence of obstruction of the biliary passages, as well as the 

 fact that the salts of the biliary acids, administered by the mouth, cause diarrhea 

 and vomiting. As, however, intestinal contractions aid absorption, the bile is, in 

 this connection also, active in taking up the dissolved food. 



The presence of bile is necessary for the normal vital activity of 

 the intestinal epithelium in the absorption of the fatty globules. 



Through its excretion the bile supplies a sufficient amount of water 

 for the feces. Animals with biliary fistulae and human beings with 

 obstructed biliary passages are markedly constipated. Besides, the 

 slippery mucus of the bile facilitates the advance of the ingesta through 

 the intestinal canal. 



