26 



GASEOUS METABOLISM OF INFANTS. 



In the combustion of 41.5 grams of carbon and 4.4 grams of hydrogen, 

 145.87 grams of oxygen are used. Deducting from this the 7.69 grams 

 originally in the protein and not excreted in the urine or feces, 138.18 

 grams of oxygen additional are required. During the process of oxida- 

 tion, 152. 17 grams of carbon dioxide are formed. Reducing these values 

 to volumes, we then have the ratio : 



Volume C0 2 77.39 



Volume 2 96.63 



= 0.801. 



The oxygen required for combustion, the products of combustion, 

 and the respiratory quotient for several typical materials have been 

 calculated and are given in table 14. 



Table 14. — Respiratory quotients for protein, fats, and carbohydrates. 



1 These values apply likewise to dextrose and levulose. 



2 While this computation is based upon meat protein, the values will be essentially the same 

 for all proteins. These values represent quantities found when burning protein not in a calori- 

 metric bomb, but in the animal body. 



3 The heat of combustion of protein averages 5.65 calories per gram; deducting the unoxidized 

 material in the urine, the heat per gram would be 4.40 calories. For discussion of this point, see 

 Atwater and Bryant, Storrs (Connecticut) Agr. Expt. Sta. Rept., 1899, p. 73. 



The carbohydrates have a respiratory quotient of 1.00; fat in general, 

 of 0.71 ; and protein of 0.81. From these factors, therefore, we can see 

 that during inanition, when the subject is subsisting for the greater 

 part upon body-fat and protein, the respiratory quotient would tend to 

 approach 0.71. On the other hand, if a diet is taken consisting largely 

 of carbohydrates, the respiratory quotient tends to approach 1.00. 



Since the metabolism of the protein remains relatively constant from 

 day to day and from hour to hour and is but a small proportion of the 

 whole, the errors involved in its calculation are not of sufficient magni- 

 tude to influence seriously any deduction drawn from the results in 

 which these calculations occur. Usually the disintegration of the 

 protein is about 1 5 per cent of the total katabolism. Magnus-Levy 1 has 

 calculated that if the remaining 85 per cent is wholly from carbo- 

 hydrates, the respiratory quotient would be 0.971 ; if, on the other hand, 

 the remainder of the energy is derived solely from fat, the respiratory 



Magnus-Levy, von Noorden's Handbuch der Pathologie des Stoffwechsels, Berlin, 1896, 1 , p. 217. 



