550 



METABOLISM 



THE MAGNITUDE OF THE RESPIRATORY EXCHANGE 



It is evident thai the amount of carbon dioxide expired and of oxy- 

 gen retained will be proportional to the energy liberation in the animal 

 body. Even at the risk of repetition it should be noted that the 

 energy exchange can be very accurately calculated from the result of 

 the materia] balance sheet — indirect calorimetry, as it is called (page 

 562). On account of the comparative simplicity of measuring the carbon 

 dioxide output and oxygen intake, it is natural that many of the obser- 

 vations that have been made on energy production in the animal body 

 depend on the use of this method, justification for which is found in the 

 complete agreement between the results of direct and indirect calorim- 

 etry in a great variety of diseases and conditions in man (Du Bois r ').* 



In the first place, it is interesting to compare the respiratory ex- 

 changes of different animals computed per kilo body weight. This is 

 shown in the following table. 



(Modified from Pembrey.) 17 



"For the convenience of those who may desire lo know more about the methods of analysis 

 that are suitable in the clinic, a chapter on the subject will be found beginning on page 554. 



