360 THE POPULAR SCIENCE MONTHLY 
PHYSIOLOGY 
. In this article, so far, we have dealt with the natural-history side of 
hibernation, explained what is meant by the various terms used in con- 
nection with this state and in what respect the condition itself differs 
in the various animals subject to its peculiar manifestations: a condi-. 
tion provided by nature to tide an animal over a period when its very 
existence, owing to scarcity of food, becomes too difficult or even impos- 
sible to maintain; so by preserving the animal’s life allows it to per- 
petuate its species. 
We will now pass on to consider the purely physiological phases and 
phenomena of this state. 
In hibernation all the activities of the body are greatly reduced, the 
temperature of the animal is lowered and even falls to a point slightly 
above that of the surrounding media. As it has been pointed out above, 
animals which hibernate do not belong to any one class, but examples 
are met with in mammals, reptiles (?), amphibians, insects, mollusce, 
but curiously enough, no case is known among birds. 
In some cases, previous to entering the hibernating state, the animal 
stores up food in its den or nest, on which it feeds when it wakes at 
intervals during its winter sleep. This is hardly pure hibernation, as 
in the true cases there is a special accumulation of fat in the animal’s 
body before the commencement of the torpid state (the animal not 
waking to feed) and this serves as food during the hibernating period. 
A peculiar physiological change is here involved—a herbivorous animal 
becomes carnivorous, this being caused by the animal living on its own 
flesh, hence the excretions (small) of the animal become profoundly and 
completely altered in their chemical characters. 
A low temperature is the cause generally assigned for the production 
of hibernation, but a more careful consideration of the facts long ago 
showed that cold could not be the sole cause of the phenomenon. Most 
observers who have worked on the subject have found that extreme cold 
will not cause an active animal to hibernate; although Saissy has ob- 
served that continued cold, and a limited amount of air for respiration 
caused a marmot to pass into a typical hibernating condition, even in 
summer. Against this we have Vernon Bailey’s experiments with 
spermophiles (first cousins of the marmots or ground-hogs), which 
showed that in the case of hibernating animals a few degrees lower 
temperature changed the torpid state into one of death. 
Mangili found that torpid marmots and bats were awakened by 
exposure to severe cold and that lessened or confined air would not cause 
hibernation. Dormice have been kept in a warm room throughout the 
winter and yet they hibernated and were not aroused when the extreme 
90°C. The warmth, however, delayed the onset of 
ths and made it less profound. Again, as has been 
bernation may take place in the dry hot season. 
temperature was 
torpidity by two mon 
mentioned before, hi 
