326 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



that the bile-acids dissolve or mix with the fats and at the same time moisten 

 the mucous membrane, and for these reasons aid in bringing the fat into 

 immediate contact with the epithelial cells. It was stated, for instance, 

 that oil rises higher in capillary tubes moistened with bile than in similar 

 tubes moistened with water, and that oil will filter more readily through 

 paper moistened with bile than through paper wet with water. Groper, 1 who 

 repeated these experiments, finds that they are erroneous. It seems 

 certain, however, that the bile-aeids enable the bile to hold in solution 

 a considerable quantity of fatty acids, and possibly this fact explains its 

 connection with fat absorption. It was formerly believed that bile is 

 also of great importance in restraining- the processes of putrefaction in 

 the intestine. It was asserted that bile is an efficient antiseptic, and 

 that this property comes into use normally in preventing excessive putre- 

 faction. 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-aeids and cholalic 

 acid do have a direct retarding effect upon putrefactions outside the body ; 

 but this action is not very pronounced, and has not been demonstrated satis- 

 factorily 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 due to 

 some 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 proteid 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. Lastly, bile takes a direct part in suspending or destroying 

 peptic digestion in the acid chyme forced from the stomach into the duodenum. 

 The chyme meeting with bile and pancreatic juice is neutralized or is made 

 alkaline, which alone would prevent further peptonization. Moreover, when 

 chyme and bile are mixed a precipitate occurs, consisting partly of proteids 

 (proteoses and syntonin) and partly of bile-acids. It is probable that pepsin, 

 according to its well-known property, is thrown down in this flocculent pre- 

 cipitate and, as it were, prepared for its destruction. 



Glycogen. — One of the most important functions of the liver is the for- 

 mation 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 iodine solutions, instead of the 

 familiar deep blue of vegetable starch, and this reaction serves to detect glyco- 

 1 Arrhiv fur Anatomie wnd Physiologic ("Physiol. Abtlieilung"), 1889, S. 505. 



