CHAPTER LXIII 



THE CARBON BALANCE 



Before proceeding to discuss the special metabolism of proteins, fats 

 and carbohydrates, it will be advantageous to consider briefly some gen- 

 eral facts concerning the excretion of carbon dioxide and the intake of 

 oxygen. In the first place, it is important to note that the extent of the 

 combustion process in the animal body is proportional to the amount of 

 oxygen absorbed and of carbon dioxide produced, whereas the nature of 

 the combustion is indicated by the ratio existing between the amounts of 

 carbon dioxide expired and of oxygen retained in the body. An investi- 

 gation of the carbon balance, in other words, is partly quantitative and 

 partly qualitative quantitative in the sense that it indicates how in- 

 tensely the body furnaces are burning, and qualitative in the sense that 

 it tells us what sort of material is being burned at the time. 



THE RESPIRATORY QUOTIENT 



Influence of Diet. The respiratory quotient is determined by com- 

 parison of the volume of carbon dioxide expired with the volume of oxy- 

 gen meanwhile retained in the body or, as a formula, 



Vol. C0 2 expired 

 Vol. 2 retained 



For the sake of brevity the respiratory quotient is often written R. Q. That 

 it serves as an indicator of the kind of combustion occurring will be evi- 

 dent from the following equations: 



1. Carbohydrate: C r H 12 O 6 + 6O, = 6CO 2 + 6H 2 O 

 (Dextrose.) 



2. Fat: CJI.(C 18 H 33 O 2 ) 3 + SOO 2 = 57CO 2 4- 52H.O 



(Olein.) 



3. Protein : C 72 H 112 N 18 O 22 S + 77O 2 = 63CO 2 + 38H 2 O + 9CO (NH 2 ) 3 + SO 3 



[Empirical formula for 

 albumin (Lieberkuhn).] , 



.-. R.Q. ^- =082 

 O a 77 



582 



