210 Metabolism of Healthy Man. 



of this disintegration of the protein, Loewy computes the portion that is oxi- 

 dized in the body as 41.5 grams of carbon, and 4.4 grams of hydrogen; the oxi- 

 dation of these two materials requires 145.87 grams of oxygen. Of the 22.68 

 grams of oxygen in the 100 grams of flesh, 14.99 grams are excreted either in 

 the urine or in the feces and thus only 7.69 grams enter into the oxidative 

 processes; the remaining 138.18 grams of oxygen necessary for the oxidation 

 must therefore be taken from the air. During the process of oxidation, 152.17 

 grams of carbon dioxide are formed. If these values are reduced to volume 



CO 77 39 

 by the well-known formulas, the ratio, then, is as follows : -~ - 2 = * = 0.801. 



^2 yb.uo 



RESPIRATORY QUOTIENT AS AN INDEX TO THE CHARACTER OF THE METABOLISM. 



Calculated Respiratory Quotients and Calorific Equivalents of Carbon Dioxide 

 and Oxygen for Protein, Fat and Carbohydrate. 



As an aid in interpreting the results of the experiments here reported and in 

 the calculations of the ratios of the carbon dioxide and oxygen to the heat, the 

 oxygen required to oxidize 1 gram of the various substances in the body material 

 or food, the products of the oxidation of 1 gram of these substances, the relation 

 of the volume of carbon dioxide eliminated and of oxygen absorbed, the number 

 of calories per gram of carbon dioxide and the number of calories per gram of 

 oxygen, i. e., their calorific equivalents, have been computed and placed in table 

 87. For carbohydrate, we have selected starch, cane sugar and glucose; for fat, 

 both animal fat and human fat are given, and fat-free, dry flesh represents the 

 protein. While there are slight mathematical differences between the results 

 presented in this table and those computed by other investigators, the values are 

 substantially correct and may be taken as representing the average protein, fat 

 and carbohydrate of either body material or food. The volumes of gases are 

 reduced to standard conditions of barometer and pressure. The heat of com- 

 bustion per gram is likewise given, and the respiratory quotient, namely, the 

 relation between the volumes of carbon dioxide eliminated and the oxygen 

 absorbed, is presented in the eighth column. Of especial significance in con- 

 nection with the calorific equivalent of carbon dioxide, i. e., the number of 

 calories accompanying the formation of 1 gram of carbon dioxide, is the large 

 difference between the values for carbohydrate and fat. On the other hand, the 

 calorific equivalent of oxygen, i. e., the number of calories accompanying the 

 absorption of 1 gram of oxygen, is practically the same whether the material 

 oxidized is carbohydrate, fat, or protein. The lowest value is for protein, but 

 as has been frequently pointed out, 1 the protein rarely exceeds 15 per cent of the 

 total energy transformation in a day. Consequently, the number of grams of 

 oxygen, if correctly measured, should give an accurate index of the total energy 

 transformation in an experimental period. 



1 See Magnus-Levy, Physiologic des Stoffwechsels, von Noorden's Handbuch der 

 Pathologie des Stoffwechsels, Berlin, 1906, 2, p. 217. 



