752 PHYSIOLOGY OF DIGESTION AND SECRETION. 



of this hydrolysis. A number of observers have shown that when a 

 permanent biliary fistula is made, and the bile is thus prevented from 

 reaching the intestinal canal, a large proportion of the fat of the food 

 escapes absorption and is found in the feces. This action of the 

 bile may be referred directly to the fact that the bile acids serve as a 

 solvent for the fats and fatty acids. It was formerly believed that 

 bile is also of great importance in restraining the processes of putre- 

 faction in the intestine. It was asserted that bile is an efficient 

 antiseptic, and that this property comes into use normally in prevent- 

 ing excessive putrefaction. Bacteriological experiments made by a 

 number of observers have shown, however, that bile itself has very 

 feeble antiseptic properties, as is indicated by the fact that it putrefies 

 readily. The free bile acids and cholalic acid do have a direct retard- 

 ing effect upon putrefactions outside the body ; but this action is not 

 very pronounced, and has not been demonstrated satisfactorily for 

 bile itself. It seems to be generally true that in cases of biliary fistula 

 the feces have a very fetid odor when meat and fat are taken in the 

 food. But the increased putrefaction in these cases may possibly be 

 an indirect result of the withdrawal of bile. It has been suggested, 

 for instance, that the deficient absorption of fat that follows upon the 

 removal of the bile results in the protein and carbohydrate material 

 becoming coated with an insoluble layer of fat, so that the penetration 

 of the digestive enzymes is retarded and greater opportunity is given 

 for the action of bacteria. We may conclude, therefore, that, while 

 there does not seem to be sufficient warrant at present for believing 

 that the bile exerts a direct antiseptic action upon the intestinal 

 contents, nevertheless its presence limits in some way the extent of 

 putrefaction. 



Glycogen. One of the most important functions of the liver is 

 the formation of glycogen. This substance was found in the liver in 

 1857 by Claude Bernard, and is one of several brilliant discoveries 

 made by him. Glycogen has the formula (C 6 H 10 O 5 ) n , which is also 

 the general formula given to vegetable starch ; glycogen is therefore 

 frequently spoken of as "animal starch." It gives, however, a port- 

 wine-red color with iodin solutions, instead of the familiar deep blue 

 of vegetable starch, and this reaction serves to detect glycogen not 

 only in its solutions, but also in the liver cells. Glycogen is readily 

 soluble in water, and the solutions have a characteristic opalescent 

 appearance. Like starch, glycogen is acted upon by ptyalin and 

 other diastatic enzymes, and the end-products are apparently the 

 same namely, maltose, or maltose and some dextrin, or else dex- 

 trose, depending upon the enzyme used. Under the influence of 

 acids it may be hydrolyzed at once to dextrose.* 



* The extensive literature of glyccgen is collected and reviewed by Cre- 

 ;ner in the " Ergebnisse der Physiologic, " vol. i, part i, 1902; and by Pfliiger, 

 f. die gesammte Physiologic," 96, 1, 1903. 



