128 RESPIRATORY EXCHANGE OF ANIMALS AND MAN 



exchange determined by Nagai himself would correspond to a forma- 

 tion of 1 3 mg. glycogen per kg. and hour or 4 gr. in 1 3 days. A 

 marmot will wake up at intervals varying between 14 and about 30 

 days and use, according to Weinland and Riehl, about 2 gr. glycogen 

 per kg. each time. The figure deduced from Nagai's respiration 

 experiments is therefore still considerably in excess of the require- 

 ments and would lead, if a formation of glycogen from fat were alone 

 responsible for the low quotients, to a very great accumulation of 

 glycogen in the body. As will be shown presently it is not at all 

 certain that glycogen is used exclusively or at all as combustion 

 material during the process of awakening. 



Nagai expresses the opinion that abnormal metabolic processes 

 and especially incomplete oxidations, are in the main responsible for 

 the low respiratory quotient during hibernation. He has shown that 

 lactic acid appears in the urine in large quantities (from 25 to 120 mg. 

 per kg. and day), that the nitrogen metabolism is only slightly 

 diminished as compared with the total metabolism and that the cata- 

 bolism of proteins becomes very incomplete. The urinary nitrogen 

 falls to while the oxygen absorption is only J^, and the CO 2 output 

 ^V of the corresponding quantities when the animal is awake but starv- 

 ing. During the sleep amino acids and urea make up respectively 

 65-6 and 17-6 per cent, of the total nitrogen, while during ordinary in- 

 anition the figures are 22 per cent, amino acids and 66 per cent. urea. 

 It has not been proved by Nagai that the incomplete oxidations, which 

 undoubtedly occur, are quantitatively sufficient to explain the low re- 

 spiratory quotients. 



It is obvious that it would not be possible to calculate the heat 

 production of hibernating animals from their respiratory exchange, and 

 a comparison between direct calorimetric experiments and respiration 

 experiments would be likely to furnish a clue to the nature of the 

 processes taking place. 



The respiratory exchange of hibernating mammals during the pro- 

 cess of awakening has been studied by Mares [1892], Dubois [1899], 

 Pembrey, Weinland and Riehl and Henriques [1911], The awakening 

 is initiated by some stimulus which may be a sudden increase or 

 decrease in the temperature of the surrounding medium, and perhaps 

 any kind of stimulus acting on the central nervous system through the 

 cutaneous senses. All observers agree that the awakening is accom- 

 panied by an enormous increase in the respiratory exchange. It is 

 believed by some (Dubois) that the liver is the seat of the increased 

 metabolism, and that it is brought about by the direct influence of 



