PHYSIOLOGY OF THE LIVER AND SPLEEN. 819 



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 (CJi^fP^\, 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.* 



Occurrence of Glycogen in the Liver. — Glycogen can be 

 detected in the liver cells microscopically. If the Uver of a dog is 

 remo\'ed twelve or fourteen hours after a hearty meal, hardened in 

 alcohol, and sectioned, the liver cells are found to contain clumps 

 of clear material w^hich give the iodin reaction for glycogen. Even 

 when distinct aggregations of the glycogen cannot be made out, its 

 presence in the cells is shown by the red reaction with iodin. By 

 this simple method one can demonstrate the important fact that the 

 amount of glycogen in the Uver increases after meals and decreases 

 again during the fasting hours, and if the fast is sufficiently prolonged 

 it may disappear altogether. This fact is, however, shown more 

 satisfactorily by quantitative determinations, by chemical means, 

 of the total glycogen present. The amount of glycogen in the 

 liver is quite variable, being influenced by such conditions as the 

 character and amount of the food, muscular exercise, body tem- 

 perature, drugs, etc. From determinations made upon various 



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

 mer in the "Ergebnisse der Physiologie," vol. 1, part i, 1902; and by Pfliiger. 

 "Archiv f. die gesammte Physiologie," 96, 1. 1903. 



