796 ANIMAL HEAT. 



The blood during hibernation has, according to most observers, 1 an 

 arterial colour in the veins ; on the other hand, Marshall Hall states that it 

 has a venous hue even in the arteries. Further details concerning the 

 circulation will be found in the works of Reeve, Edwards, Barkow, Horvath, 

 and Dubois. 2 



The gases in the blood of hibernating and of active marmots have been 

 determined by Dubois, 3 who found that during hibernation the arterial blood 

 contained as much oxygen, the venous blood less oxygen, and both arterial 

 and venous blood an excessive quantity of carbon dioxide, as compared with 

 the gases of arterial and venous blood from active animals. 



Digestion. The activity of the digestive organs varies according to the 

 habits of the different animals ; some, such as bats, take no food during the 

 winter; others, such as the dormouse,hamster, and marmot, store up food, 

 which they consume during short periods of activity. 4 



Nervous system. The excitability of the nervous system is greatly 

 depressed, and the nervous and other tissues of the body resemble those of 

 cold-blooded animals, in retaining their excitability for a long time after 

 removal from the body. 4 



Temperature. During hibernation the temperature resembles that of a 

 cold-blooded animal, rising and falling with that of the surroundings. In 

 this way the rectal temperature may fall as low as 2 without injurious effects 

 following. When the animal awakes from hibernation its temperature 

 generally rises rapidly many degrees above that of the air ; the most rapid rise 

 takes place after the rectal temperature has reached 17, when there may be 

 a further rise to 32 in. forty minutes ; this is accompanied by an increase in 

 the activity of the animal, and in the output of carbon dioxide. 5 



If the animal be fully awake and active, its temperature resembles that of a 

 warm-blooded animal; a fall in external temperature increases its activity, 

 temperature, and respiratory exchange, while a considerable rise has the 

 opposite effect. 6 



The power of heat regulation in hibernating animals. The capacity for 

 maintaining a constant temperature varies according to the condition of the 

 animal ; during well-marked hibernation this power is very slight, and resembles 

 that of a cold-blooded animal, but when the animal is active its power of 

 regulating its temperature is comparable to that of a warm-blooded animal. 



There is an intermediate stage when the animal is listless and inactive, 

 with a bodily temperature below that of its normal in summer, but considerably 

 above that of its surroundings. In this condition its power of regulation 

 resembles that of an immature mammal ; within certain narrow limits it is able 

 to maintain its temperature, but when exposed to cold its temperature falls, 

 and it passes into a cold-blooded condition. 7 



The awakening from hibernation. One of the most interesting phenomena 

 in hibernation is the sudden rise in temperature which occurs when the animal 

 awakes from its torpor. This rise is so great and sudden that there is 

 nothing comparable to it, not even the sudden rise seen in some cases of fever. 

 Thus Horvath 8 found the temperature of a sisel rise from 14 to 32 in 

 one hour and forty minutes, the temperature of the air remaining 1 4. In the 



1 In addition to other references, see Bernard, "Le9ons sur la chaleur animale," 1876, 

 p. 374. 



2 See references on pp. 794-795. 



3 Compt. rend. Soc. de biol., Paris, 1894, 22 decembre. 



4 For further details see the works mentioned on p. 794; also Gavarret, " De la 

 clialeur produite par les etres vivants," Paris, 1855, p. 466. 



5 Horvath, loc. cit. ; Pembrey and Hale White, loc. tit. 



6 Pembrey and Hale White, loc. cit.; Hunter, "Works," Palmer's' Edition, London, 

 1837, vol. iv. pp. 141-145. 



7 Pembrey and Hale White, loc. tit. 



8 Verhandl. d. phys.-mcd. Gcsellsch. in Wiirzburg, 1878, Bd. xii. S. 162. 



