HIBERNATION AND ALLIED STATES IN ANIMALS 109 
in a tank in which the water is being continually 
renewed by a slow stream. They are not fed. None 
of the frogs seem to pass into a condition of true 
hibernation, but they descend to the bottom of the 
tank and remain quiet, as if asleep or partially torpid, 
as, indeed, I know they often are for hours. In this 
is an interesting modification of that most profound 
torpor which they experience when buried in the mud 
of ponds. 
Even in the winter life of a creature like the marmot 
we may have all degrees of drowsiness or torpor, as I 
have shown, and it is not to be forgotten that our 
own daily sleep has its degrees, so that the night’s 
sleep may be represented by a curve with a sharp 
rise and very gradual fall, which may, as we all know, 
be greatly modified by circumstances. 
The same laws seem to apply to all the known cases 
of human lethargy, hibernation, sleep, or whatever the 
state may be called. In the case of the buried sheep 
and hogs the protective value of the condition is 
evident, as also in the case of the lethargic woman. 
This individual, with so ill-balanced and unstaple a 
constitution, would probably have been carried off by 
some form of actual disease long before, had she 
remained awake. She could exist as a mere vegeta- 
tive organism, but not as a normal human being in the 
ordinary struggle for existence. One thing which has 
been much impressed upon me by my studies of this 
whole subject, is the varying degrees of sensitiveness to 
temperature and meteorological conditions in different 
eroups of animals and different individuals of the same 
group. The bat as compared with the marmot, for 
example, may be worked like a machine by varying the 
temperature. On the contrary, the degree to which the 
woodchuck is independent of temperature was a 
surprise to me after my experience with the bat. But 
