CHAP, iv.] METABOLIC PROCESSES OF THE BODY. 563 



go on after death is carried out by some action of the liver, 

 probably of the hepatic cell itself, which is done away with by 

 a temperature of 100 C., but which is not the action of a 

 ferment capable of being isolated. 



359. We have used above the phrase ' well-fed ' animal 

 because the amount of glycogen present in the liver of an aminal 

 at any one time is very variable, and especially dependent 011 the 

 amount and nature of the food previously taken. When all food 

 is withheld from an animal, the glycogen in the liver diminishes, 

 rapidly at first, but more slowly afterwards. Even after some 

 days' starvation a small quantity is frequently still found; but 

 hi rabbits, at all events, the whole may eventually disappear. 



If an animal, after having been starved until its liver may 

 be assumed to be free or almost free from glycogen, be fed on 

 a diet rich in carbohydrates or on one consisting exclusively of 

 carbohydrates, the liver will in a short time be found to contain 

 a very large quantity of glycogen. Obviously the presence of 

 carbohydrates in food leads to an accumulation of glycogen in the 

 liver; and this is true both of starch and of dextrin and of the 

 various forms of sugar, cane, grape and milk sugar. The effect 

 may be quite a rapid one, for glycogen has been found in the 

 liver in considerable quantity within a few hours after the intro- 

 duction of sugar into the alimentary canal of a starving aminal. 



If an animal, similarly starved, be fed on an exclusively meat 

 diet a certain amount of glycogen is found in the liver. This 

 appears to be especially the case with dogs (probably with other 

 carnivorous animals also); and in earlier works on the subject 

 the constant presence of glycogen in the livers of dogs fed on 

 meat was regarded as an important indication of the formation 

 within the body of non-nitrogenous from nitrogenous material. 

 But in the first place, the quantity of glycogen thus stored up 

 in the liver as the result of a meat diet, is much less than that 

 which follows upon a carbohydrate diet; and in the second 

 place, ordinary meat, especially horse-flesh on which dogs in 

 such experiments are usually fed, contains in itself ( 59) a 

 certain amount either of glycogen or some form of sugar. 

 Moreover when animals are fed not on meat but on purified 

 proteid, such as fibrin, casein or albumin, the quantity of 

 glycogen in the liver becomes still smaller, though according to 

 most observers remaining greater than during starvation. We 

 may infer therefore that part of the glycogen which appears in 

 the liver after a meat diet is really due to carbohydrate mate- 

 rials present in the meat. Part, however, would appear to be 

 the result of the actual proteid food; and we have similar evi- 

 dence that gelatine taken as food leads to the formation of some 

 glycogen in the liver. But in this respect these nitrogenous 

 substances fall far short of carbohydrate material. 



With regard to fats, all observers are agreed that these lead 



