144 METABOLISM 



in twenty-four hours. Under constant conditions it is constant 

 in the same individual. As has already been mentioned under 

 urea, a uricolytic ferment is responsible for a considerable 

 destruction of uric acid, which then leaves the body as urea. 

 An absence of this ferment is supposed to be one of the factors 

 in the production of gout. 



The Formation of Hippuric Acid. This constituent of the 

 urine is of interest because it is formed by the kidney. If 

 this organ be perfused with blood to which benzoic acid and 

 glycin have been added, hippuric acid is produced. A ferment 

 is supposed to be concerned in this reaction. Normally, most 

 of the benzoic acid is derived from an aromatic nucleus in 

 vegetable food, but in some animals the body tissues also serve 

 as a source. Glycin is known to be a product of the metabolism 

 of proteins and is also a constituent of glycocholic acid of the 

 bile. 



The Formation of Kreatinin. Some kreatinin is, no doubt, 

 derived from the kreatin of food ingested. Of the remainder 

 excreted there is reason to believe that it represents the nitrogen 

 given off in the wear and tear of the bodily machinery. Dur- 

 ing muscular work the elimination of kreatinin is increased. 

 The amount excreted by different persons is related to the 

 weight of the active tissue in the body. There are ferments 

 in the body which have the power of changing kreatin to 

 kreatinin and other ferments which destroy both. 



Metabolism of Carbohydrates. The main facts in the 

 history of carbohydrate foodstuffs may be briefly stated. The 

 digestive processes have converted them mainly, if not entirely, 

 into dextrose. During digestion, particularly after a carbo- 

 hydrate meal, the portal blood holds more dextrose than is 

 present in blood generally. In fact, portal blood contains more 

 dextrose than the hepatic vein, indicating that some of the 

 sugar (12 to 20 per cent.) disappears during the passage of 

 the blood through the liver. It is stored in the liver as glycogen ; 

 as such it may be visible microscopically, and from which 

 it may be extracted with boiling water. If after the death of 

 the animal the liver be left in place for some time, no glycogen 

 can be extracted, but sugar is present in abundance. During 

 the intervals of digestion sugar in the hepatic vein is twice 

 as abundant as the sugar in blood generally or in that of the 



