CHAPTER XII 

 BILE 



THE bile is secreted continuously by the liver and passes into the 

 intestine through the common bile duct which opens near the pylorus. 

 Bile is not secreted continuously into the intestine. In a fasting animal 

 no bile enters the intestine, but when food is taken the bile begins to 

 flow; the length of time elapsing between the ingestion of the food and 

 the secretion of the bile as well as the qualitative and quantitative char- 

 acteristics of the secretion depending upon the nature of the food ingested. 

 Fats, the extractives of meat and the protein end-products of gas- 

 tric digestion (proteoses and peptones), cause a copious secretion of bile, 

 whereas such substances as water, acids and boiled starch paste fail 

 to do so. In general a rich protein diet is supposed to increase the 

 amount of bile secreted, whereas a carbohydrate diet would cause a 

 much less decided increase and might even tend to decrease the amount. 

 It has been demonstrated by Bayliss and Starling that the secretion of 

 bile is under the control of the same mechanism that regulates the flow 

 of pancreatic juice (see page 185). In other words, the hydrochloric 

 acid of the chyme, as it enters the duodenum transforms prosecretin 

 into secretin and this in turn enters the circulation, is carried to the 

 liver, and stimulates the bile-forming mechanism to increased activity. 



We may look upon the bile as an excretion as well as a secretion. In 

 the fulfillment of its excretory function it passes such bodies as lecithin, 

 metallic substances, cholesterol, and the decomposition products of 

 hemoglobin into the intestine and in this way aids in removing them 

 from the organism. The bile assists materially in the absorption of 

 fats from the intestine by its solvent action on the fatty acids formed 

 by the action of the pancreatic juice. 



The bile is a ropy, viscid substance which is usually alkaline in reac- 

 tion to litmus, 1 and ordinarily possesses a decidedly bitter taste. It varies 

 in color in the different animals, the principal variations being yellow, 

 brown and green. Fresh human bile from the living organism ordi- 

 narily has a green or golden-yellow color. Post-mortem bile is variable 

 in color. It is very difficult to determine accurately the amount of 

 normal bile secreted during any given period. For an adult man it 



1 It does not contain more than a slight excess of hydroxyl ions, however. 



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