918 



METABOLISM. 



and a non-nitrogenous part. The potential energy set free immediately 

 as heat in the combustion of the nitrogenous part, which is quantitatively 

 used within the region of the chemical heat regulation but is otherwise 

 lost, has been called the specific dynamic action by RuBNER. 1 The 

 remainder of the energy which is represented by the non-nitrogenous 

 part of the proteins, serves, like all other foodstuffs, in satisfying the 

 energy requirement of the cells. According to RUBNER only non-nitrog- 

 enous groups (of the proteins, fats and carbohydrates) come almost 

 entirely, if not completely, in consideration for purposes of energy. 



In close relation to the second purpose, the betterment of the condi- 

 tion of the cells, stands the question as to the conditions favoring the deposi- 

 tion of flesh in the body, which is closely associated with the question as 

 to the conditions of fattening the body. In this connection it must be 

 remembered in the first place that all fattening presupposes an overfeed- 

 ing, i.e., a supply of foodstuffs which is greater than that catabolized in 

 the same time. 



In carnivora a flesh deposition may take place on the exclusive feeding 

 with meat. This is not generally large in proportion to the quantity of 

 protein catabolized. In man and herbivora, who cannot cover their 

 calorific needs by protein alone, this is not possible, and the question as 

 to the conditions of fattening with a mixed diet is of importance. 



These conditions have also been studied in carnivora, and here, as 

 VOIT has shown, the relation between protein and fat (and carbo- 

 hydrates) is of great importance. If much fat is given in proportion 

 to the protein of the food, as with average quantities of meat with con- 

 siderable addition of fat, then nitrogenous equilibrium is but slowly 

 attained and the daily deposit of flesh, though not large, is quite constant, 

 and may become greater in the course of time. If, on the contrary, 

 much meat besides proportionately little fat is given, then the deposit 

 of protein with increased catabolism is smaller day by day, and nitrog- 

 enous equilibrium is attained in a few days. In spite of the somewhat 

 larger deposit per diem, the total flesh deposit is not considerable in 

 these cases. The following experiment of VOIT may serve as example: 



The greatest absolute deposition of flesh in the body was obtained in 

 these cases with only 500 grams of meat and 250 grams of fat, and even 



1 Rubner, 1. c., and Gesetze des Energieverbrauches, 70. 



