222 INTESTINAL DIGESTION 



Bernard and others, who have discharged all the bile by a fistula into 

 the gall-bladder, communication between the bile-duct and the duodenum 

 having been cut off, show that dogs operated on in this way have a 

 voracious appetite, but die of inanition after having lost four-tenths of 

 the body-weight. ' The following is an example of experiments of this 

 kind (Flint, 1861): A fistula was made into the gall-bladder of a dog, 

 after excising a great part of the common bile-duct. The animal 

 suffered no immediate effects from the operation, but died at the end of 

 thirty-eight days, having lost 37 J per cent in weight. He had a vora- 

 cious appetite, was fed as much as he would eat, was protected from 

 cold and was carefully prevented from licking the bile. During the 

 progress of the experiment, various observations were made on the flow 

 of bile. During the last five or six days, the animal was ravenous but 

 was not allowed to eat all that he would at one time. At that time he 

 was fed twice a day, but he would not eat fat, even when very hungry. 

 During the last day, when too weak to stanpl, he attempted to eat while 

 lying down. 



Human bile is moderately viscid, of a dark golden-brown color, an 

 alkaline reaction and a specific gravity of about 1028. Among other 

 constituents which will be described in connection with the physiology 

 of secretion it contains sodium united with two acids peculiar to 

 the bile, called glycocholic and taurocholic acids. Sodium taurocho- 

 late is much more abundant than the glycocholate. The viscidity of 

 the bile is due to mucus derived in part from the lining membrane of 

 the gall-bladder and in part, probably, from little racemose glands 

 attached to the larger bile-ducts in the substance of the liver. The 

 so-called biliary salts, sodium taurocholate and sodium glycocholate, are 

 probably the constituents of the bile that are concerned in digestion. 



Although the bile is constantly discharged in certain quantity into 

 the duodenum, its flow presents marked variations corresponding with 

 certain stages of the digestive process. In fasting animals, the gall- 

 bladder is distended with bile ; but in animals opened soon after feeding, 

 it is nearly always found empty. The actual secretion of bile by the 

 liver also is influenced by digestion. 



Disregarding slight variations, it may be stated, in general terms, 

 that the bile begins to increase in quantity immediately after eating ; 

 that its flow is at its maximum from the second to the eighth hour, dur- 

 ing which time the quantity does not vary to any great extent ; after the 

 eighth hour it begins to diminish, and from the twelfth hour to the time 

 of feeding it is at its minimum. 



One of the uses which has been ascribed to the bile is that of stimu- 

 lating peristaltic movements of the small intestine and of preventing 



