NORMAL PROCESSES OF ENERGY METABOLISM 563 



deduction made from the total oxygen absorbed. The method follows: 

 Let a be any R. Q. less than 1.0. Then Vol. CO 2 = a Vol. O 2 . Let x 

 be the part of O 2 used in combustion of carbohydrate, and Vol. O 2 x the 

 part utilized in combustion of fat. Then Vol. CO 2 x is the CO 2 

 resulting from combustion of fat. The R. Q. of fat being 0.7 it follows 



Vol. CO 2 x Vol. 2 x 



that- ^ =0.7 or, a - = 0.7. From which 



Vol. O 2 x Vol. O 2 x 



(0 0.7) Vol. O 2 ,. 



x == which is the quantity of O 2 utilized in combustion 



O.o 



of carbohydrate. The remainder, Vol. O 2 x = - is the 



O.o 



part used in combustion of fat. Calling this value y we have : for carbo- 

 hydrate x = -^ - and for fat y = TT^- For example where a is 

 O.o O.o 



2 1 



0.9 x = - and y = -. The thermal quotient of oxygen at and 

 o o 



2 



760 (page 556) would then be 5.09 X ~ + 4.7 = 4.96 Cal. per liter, or, 



3 



4.65 Cal. per liter at 18 C. 



A single example of the use of the respiratory quotient for calculation 

 of the heat production by means of the thermal quotient for oxygen will be 

 given. Lefevre(/) separated the inspired air from the expired air of a 

 subject in complete muscular repose by means of a pair of Miiller valves 

 (page 533). The expired air was measured and subsequently analyzed. 

 In a one-hour period the amount of oxygen absorbed measured at 18 C. 

 was 13.73 liters. The R. Q. was 0.89, which the author states corre- 

 sponds to a combustion in which out of three molecules of oxygen absorbed, 

 two served for oxidation of carbohydrate and one for oxidation of fat. 

 The mean thermal quotient then would be 4.77 X 2 -J- 4.41 = 4.65 Cal. 

 per liter. The heat production was (13.73 X 4.65 ==) 63.8 Cal. per hour 

 or about 1500 Cal. in 24 hours. This minimal metabolism was confirmed 

 by Lefevre by direct calorimetry. It corresponds well with later determin- 

 ations of the basal metabolism (see page 607). 



4. Calculation of Heat Production from the Respiratory Exchange 

 and the Urinary Nitrogen. The method outlined above even when the 

 respiratory quotient is known is defective in that it does not take ac- 

 count of the protein metabolism which is always taking place. Apparently 

 the first to attempt an improvement of the method by making allowance 

 for the protein metabolism was Kauffmann. His paper was followed 

 three months later by one from Laulanie who had developed similar im- 

 provements quite independently. 



a. The Method of Successive Thermal Quotients. Instead of relying 

 upon a mean thermal quotient for oxygen which answers very well for 



