STATISTICS OF NUTRITION. 683 



while a body rich in fat, since it needs and destroys less albumen, must 

 draw on its store of fat. Young animals, since they are thin, therefore 

 need more albumen and fat than older ones, while young animals, to 

 fatten, require more food than older ones. It is also easier to fatten thin 

 animals than to make tolerably fat animals still fatter. 



(e) Feeding with Carbohydrates. — The action of the carbohydrates 

 in nutrition is especially seen in the herbivora, which are incapable of 

 being supported with albumen alone or with albumen and fat. Experi- 

 ment has shown that in so far as they are digestible all carbohydrates 

 have the same influence on the metabolism of the body. This applies to 

 starch, cane-, grape-, and milk-sugar, dextrin, and, to a certain extent, to 

 cellulose. 



It is generally assumed that all the carbohydrates which enter the 

 animal body unite with the oxygen obtained in inspiration to, form C0 2 

 and HjO, so that an increase in carbohydrate diet means an increase in the 

 C0 2 of the expired air. This is not, however, universally true, since 

 under many circumstances the carbohydrates may be retained in the 

 body as fat; on the other hand, it cannot be positively stated whether 

 the carbohydrates which are converted into sugar in digestion are 

 directly oxidized as sugar, or are all first converted into glycogen. 



Feeding dogs exclusively with carbohj'drates has proven that the 

 destruction of tissue-albumen and fat is under such circumstances less 

 than when the animal is deprived of all food, but that the destruction 

 of albumen is constant, and that such animals finally perish from 

 inanition. If albumen is given together with the carbohydrates in 

 increasing quantities, the excretion of nitrogen increases correspond- 

 ingly, but in a much less degree than when albumen alone or albumen 

 and fat constitute the diet ; therefore the carbohydrates in food serve to 

 spare the tissue change in proteids to a greater extent even than fat. 

 Hence, to keep the body in a state of nutritive balance a moderately 

 small amount of albumen is required with a large amount of carbo- 

 hydrates, and, as a consequence, the herbivora are kept in good nutrition 

 with the small amount of albumen found in their food. If the smallest 

 amount of albumen is given with the corresponding amount of carbo- 

 hydrates under which the body weight may be maintained without losing 

 albumen or fat, and then the albumen of the food is increased, the 

 elimination of nitrogen is also increased, but to a less degree than if 

 albumen was given alone ; there is, therefore, now an increase in the 

 albumen and fat of the body. If, now, the amount of carbohydrates 

 is increased without diminishing the quantity of albumen in the food, 

 fat then accumulates in the body; and if the albumen is also increased 

 both albumen and fat accumulate. 



It is not yet quite clear whether this fat is formed from the carbon 



