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. 1 
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. 1 '' 
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." 
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, "Lecons sur la chaleur animale," 1876, 
p. 374. 
2 See references on pp. 794-795. 
3 Compt. rend. Soc. dc biol., Paris, 1894, 22 dt;ceml>re. 
4 For further details see the works mentioned on p. 794 ; also Gavarret, " De la 
chaleur produite par lea litres vivants," Paris, 1S55, p. 466. 
5 Horvath, loc. cit. ; Pembrey and Hale White, loc. cit. 
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. cit. 
8 Verhandl. d. phys.-med. Gesellsch. in Wurzburg, 1S78, Bd. xii. S. 162. 
