860 HIBERNATION. [BOOK n. 



hepatic glycogen of the winter frog ( 455). The fat thus stored 

 up before the approach of winter serves as the main supply of 

 material for metabolism in the winter sleep. Since during the 

 whole hibernating period some amount, at least, of oxygen is 

 at the command of the tissues, we have no reason to think that 

 the metabolism of hibernation is fundamentally different from the 

 metabolism of ordinary life, or that the stored up fat suffers changes 

 and gives rise to energy in other ways than by the oxidation 

 which fat in an ordinary way undergoes in the body. Nevertheless 

 a detailed study of the metabolism of hibernation accompanied by 

 direct calorimetric observations would probably disclose interesting 

 results. 



