CHEMICAL COMPOSITION OF THE LIVER-CELLS. 263 



parts of the liver. Like inulin, it gives a deep red colour with solution of iodine 

 in iodide of potassium. It is changed into dextrin and sugar by diastatic ferments, 

 and when boiled with dilute mineral acids, it yields grape-sugar ( 148, I.; 170, 

 L; 252, III.). 



Preparation of Glycogen. [Feed a rabbit on carrots or boiled rice, and kill it three or four 

 hours thereafter. Kemove the liver immediately after death, cut it into fine pieces, and place 

 these in boiling water, and boil it for some time in order to obtain a watery extract of the liver. 

 The boiling water destroys the ferment supposed to be present in the liver, which would transform 

 the glycogen into grape-sugar. To the cold filtrate are added alternately dilute hydrochloric acid 

 and potassio-mercuric iodide, which precipitates the proteids. Filter, when a clear opalescent 

 fluid, containing the glycogen in solution, is obtained. The glycogen is precipitated from the 

 filtrate, as a white amorphous powder, on adding an excess of 70 to 80 per cent, alcohol. The 

 precipitate is washed with 60 per cent, and afterwards with 95 per cent, alcohol, then with ether, 

 and lastly, with absolute alcohol ; it is dried over sulphuric acid and weighed (Brilcke). Kiilz 

 modifies the method somewhat. After boiling the liver for half an hour, it is rubbed up with 

 liquor potassse (100 grm. liver, 4 grm. KHO). Evaporate in the water-bath until all is dissolved, 

 which occurs in about 3 hours. After cooling, neutralise with HC1 and precipitate the proteids 

 as above. F. Eves asserts that the post-mortem conversion of sugar in the liver is not attribut- 

 able to a ferment action, and the rapid appearance of sugar in the liver after death is due to the 

 specific metabolic activity of the dying cells.] 



Sources. The " mother-substance " of the glycogen of the liver has been 

 variously stated to be the carbohydrates of the food {Pavy) ; fats (olive oil, 

 Salomon) ; glycerine, taurin, and glycin (the latter splitting into glycogen and urea), 

 the proteids (CI. Bernard) ; and gelatin (Salomon). If it is derived from the 

 albumins, it must be formed from a non-nitrogenous derivative thereof. 



Rohmann found that the use of ammonia carbonate and asparagin or glycin, along with a 

 carbohydrate diet, in rabbits considerably increased the formation of glycogen. The excessive 

 formation of acid observed by Stadelmann in diabetes unites with the ammonia and diminishes 

 considerably the formation of glycogen. 



Effects of Food. Rabbits, whose livers have been rendered free from glycogen 

 by starvation, yield new glycogen from their livers when they are fed with cane- 

 sugar, grape-sugar, maltose, or starch. Forced muscular movements soon make 

 the liver of dogs free from glycogen, exposure to cold diminishes its amount. 

 Dextrin and grape-sugar occur in the dead liver, but, in addition, some glycogen is 

 found for a considerable time after death in the liver and in the muscles. 



If glycogen is injected into the blood, achroodextrin appears in the urine, and also 

 haemoglobin, as glycogen dissolves red blood-corpuscles. Ligature of the bile-duct causes 

 decrease of the glycogen in the liver. 



Other Situations. Glycogen is not confined to the liver-cells; it occurs during foetal life 

 in all the tissues of the body of the embyro [including the embryonic skeleton], in young 

 animals (Kilhne), the placenta {Bernard). [It occurs in large amount in the liver during intra- 

 uterine life.] In the adult it occurs in the testicle, in the muscles (MacDonnel, O. Nasse), in 

 numerous pathological products, in inflamed lungs (Kilhne), and also in the corresponding 

 tissues of the lower animals. [It also occurs in the chorionic villi, in colourless blood- 

 corpuscles, in fresh pus cells which still exhibit amoeboid movements, and in fact in all 

 developing animal cells, with amoeboid movement ; it is a never-failing constituent in cartilage, 

 and in the muscles and liver of invertebrata, such as the oyster. There is none in the fresh 

 brain of the dog or rabbit, but it is found in the brain in diabetic coma (Abeles).] 



Modifying Conditions. If large quantities of starch, milk-, fruit-, or cane-sugar, 

 or glycerine, but not mannite, or glycol, or inosite, be added to the proteids of the 

 food, the amount of glycogen in the liver is very greatly increased (to 12 per cent, 

 in the fowl), while a purely albuminous or purely fatty diet diminishes it enor- 

 mously. During hunger it almost disappears. * The injection of dissolved carbo- 

 hydrates into a mesenteric vein of a starving rabbit causes the liver, previously free 

 from glycogen, to contain glycogen. 



[Effect of Drugs. Arsenic, phosphorus, and antimony destroy the glycogenic function of the 

 liver, no glycogen being present in the liver in animals poisoned with these drugs, so that 

 puncture of the floor of the fourth ventricle no longer causes glycosuria in them. In animals 

 poisoned by strychnia or curara, it is greatly diminished, both in the liver and in the muscles. 

 Sugar is always present in the urine in the latter case but not in the former.] 



