678 ANIMAL HEAT 



All the modern respiration calorimeters permit the direct estimation 

 not only of the carbon dioxide produced, but also of the oxygen con- 

 sumed. This allows the amount of heat to be calculated indirectly 

 (so-called indirect calorimetry), as well as measured directly. For if we 

 know how much of the oxygen taken in goes to oxidize protein, fat and 

 carbohydrates, respectively, we can calculate the amount of heat pro- 

 duced in the body with a given consumption of oxygen. The amount of 

 protein oxidized is easily obtained from the nitrogen excretion. The 

 respiratory quotient (corrected for the influence of the protein meta- 

 bolized) informs us, with certain limitations, as to the proportions of fat 



Fig. 222. Clinical Respiration Calorimeter. The patient is shown on the bed half 

 way in. The tube of a stethoscope strapped over the heart is seen. Coiled up 

 on the wall is the (electric resistance) rectal thermometer not yet inserted. To 

 the right of this is shown a telephone for communicating with the patient if 

 necessary (Lusk, et a/.). 



and carbohydrates being consumed. Thus, a respiratory quotient of 

 0-70 represents the oxidation of fat alone, a quotient of i-oo the oxida- 

 tion of carbohydrate alone (p. 241). 



If the respiratory quotient is intermediate between these extremes 

 e.g., 0-85, it would represent the oxidation of fat and carbohydrate in 

 such a proportion that 49 per cent, of the number of calories produced 

 are due to the burning of carbohydrate, and 51 per cent, to the oxidation 

 of fat. With this respiratory quotient, the absorption of i litre of 

 oxygen would indicate that 4,863 gram-calories had been produced in the 

 body. In a similar way the amount of heat produced can be calculated, 



