364 THE POPULAR SCIENCE MONTHLY 
hibernating animal does not keep much above it, until a point is 
reached when the animal wakens. Then its temperature rushes up 
many degrees in a few minutes and at the same time the excretion of 
carbon dioxide becomes enormously increased. 
IMMUNITY AND FoRMATION OF ANTITOXINE 
Hansmann describes the influence of temperature on the incubation 
period and the formation of antitoxine. He found much greater resis- 
tance to infection and lengthened incubation time and no production of 
the various antibodies during hibernation. Blanchard and Blatin made 
the observation that in the hibernating condition the marmot was im- 
mune to parasitic maladies. 
CoNCLUSION 
It may be stated and accepted that when hibernation has been fully 
investigated, all degrees of cessation of functional activity of the vari- 
ous organs and tissues will be found represented, from the normal sleep 
of man and other animals to the lowest degree of activity manifested 
in life. Though some observers claim that in true hibernation there is 
complete cessation of function in some organs, as, for example, the 
lungs and movements of respiration, this is extremely doubtful. The 
awakening of an animal from its winter sleep is never sudden, but 
slow and gradual, often lasting for hours. This gradation from a pas- 
sive to an active condition is no doubt protective to the vital machinery, 
as it has been noticed that when bats have been awakened suddenly they 
have quickly died. 
We have spoken of hibernation in man, and by some authorities, 
sleep in man is closely allied to a state of hibernation. Natural daily 
sleep is favored by moderate exhaustion, the cravings of hunger being 
satisfied, and the absence of all peripheral stimuli. Sleep is a rhythmic 
diminution of the activities of all the tissues, but especially of the 
nervous system, which has control of all the others. As we have men- 
tioned before, Marshall Hall and others have shown that the gaseous 
interchange in a hibernating animal is greatly lessened and so too it is 
in sleep. It has also been shown by experiments that hibernation, like 
daily sleep, is not a series of fixed and rigid phenomena, but is varied 
in depth and in season and its main use is that of protecting and con- 
serving life. 
All forms of profound winter and summer sleep are protective, both 
of the individual and of the species. If it were not for this act of 
hibernation, many of the mammalia, amphibia, as well as some other 
groups of animals, would be utterly destroyed from the face of the 
earth. 
