3/2 USES OF THE LIVER DUCTLESS GLANDS 



the separation of cholesterin from the blood and its discharge in the 

 feces in the form of stercorin, may be regarded as established, as well 

 as the existence of cholesteremia as a definite pathological condition 

 (Flint, 1862). 



FORMATION OF GLYCOGEN IN THE LIVER 



In addition to the uses of the liver already described, this organ con- 

 stantly contains in health a substance resembling starch, called glyco- 

 gen, which is converted into glucose and is carried into the circulation 

 by the hepatic veins. 



Glycogen belongs to the class of carbohydrates, is isomeric with 

 starch and is readily converted into glucose. In nearly all regards it has 

 the properties of starch, but it gives a deep red color with iodin instead 

 of a blue. In the liver-cells it exists in the form of amorphous granules 

 surrounding the nuclei. It may be extracted from a decoction of the 

 liver-substance, precipitating the albuminous matters by adding alter- 

 nately dilute hydrochloric acid and potassio-mercuric iodide, filtering and 

 treating the filtrate with an excess of alcohol. The alcoholic precipitate, 

 washed with alcohol and dried rapidly, is in the form of a white powder 

 that will keep indefinitely. In the adult, glycogen is most abundant 

 in the liver ; but it has been found in small quantity in the muscular 

 substance, in cartilage and in certain cells in process of development. 

 In the early months of foetal life it exists in nearly all the tissues and 

 is found, also, in cells attached to the villi of the placenta. 



The most important of the conditions that influence the quantity of 

 glycogen in the liver relate to alimentation and digestion. The liver 

 always contains more glycogen during digestion than fasting. After a 

 few days of starvation, glycogen may almost or quite disappear from 

 the liver. This also occurs in animals fed for a time exclusively with 

 fats, and the quantity is diminished by a purely albuminous diet as con- 

 trasted with a mixed diet. Still, glycogen is invariably present in the 

 livers of healthy carnivorous animals that have always been fed with 

 meat alone. 



A great increase in the quantity of glycogen in the liver is produced 

 by feeding animals largely with carbohydrates. Not only are the starches 

 apparently stored up for a time in the form of glycogen in the liver, but 

 sugars undergo a change into glycogen, which accumulates in the liver. 

 This is to be expected, as the starches are changed into sugar before 

 they are absorbed and all the carbohydrates behave in the same way as 

 regards general nutrition. 



So far as regards the influence of alimentation on the formation of 

 glycogen, it seems probable that in the herbivora and in man, the chief 



