252 



INTESTINAL DIGESTION. 



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 nearly the whole 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 per 

 cent, in weight. He had a voracious 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 hun- 

 gry. During the last day, when too weak to stand, he attempted to eat while 

 lying down. 



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

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

 stituents, which will be described in connection with the physiology of secre- 

 tion, it contains sodium united with two acids peculiar to the bile, called 

 glycocholic and taurocholic acids. Sodium taurocholate is much more abun- 

 dant than the glycocholate. The viscidity of the bile is due to mucus de- 

 rived 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 which are con- 

 cerned 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 dis- 

 tended with bile ; but in animals opened soon after feeding, it is nearly always 

 found empty. The actual secretion of bile by the liver is also influenced by 

 digestion. The following table gives the variations observed in the dog with 

 a biliary fistula : 



TABLE OF VARIATIONS IN THE FLOW OF BILE WITH DIGESTION. 



(At each observation the bile was drawn for thirty minutes.) 



