152 GENERAL METABOLISM 



Here, then, is an indirect means of arriving at the 

 energy production. Though simpler to work than the 

 direct method, it is not free from certain fallacies. The 

 first of these is that the actual production of COg may 

 not correspond to the ehmination, owing to the capacity 

 of the tissues for storing this gas. A second fallacy is 

 that processes other than direct utihsation of the food- 

 stuffs may conceivably be taking place. Supposing, for 

 instance, that the body is storing fats after forming them 

 from carbohydrates. In the conversion of an oxygen-rich 

 into an oxygen-poor compound a certain amount of oxygen 

 is hberated, and is presumably available for oxidation of 

 other molecules. The consequence is that the amount of 

 atmospheric oxygen needed by the tissues is diminished 

 to a corresponding extent. In other words there will be 

 an elevation of the R.Q. The abnormally high respiratory 

 quotients (1-2 or 1-3) observed in hibernating animals at 

 the onset of the dormant period, and in geese when 

 they are fed with large quantities of carbohydrates, have 

 been taken to prove the conversion of carbohydrate into 

 fat. 



A third fallacy lies in the fact that COg may be produced 

 by processes other than oxidation in the tissues. In 

 herbivorous animals a large amount of COg is formed in 

 the intestine by bacterial decomposition. 



Intestinal fermentation, then, and conversion of carbo- 

 hydrate into fat, will both tend to raise the R.Q. Both 

 factors are probably concerned in the abnormally high 

 values found at the onset of hibernation. 



Under certain circumstances a respiratory quotient of 

 abnormally low value has been obtained, particularly at 

 the end of hibernation. The meaning of this is not clear. 

 It has been ascribed to a conversion of fat into glycogen, 

 which is stored preparatory to awakening. It is doubtful, 

 however, whether the amount of carbohydrate thus formed 

 is sufficient to account for the retention of so much oxygen. 

 Further, the low R.Q. may be due to other causes, as, for 



