5s ANIMAL INTELLIGENCE 
periods of hibernation followed by intervals of con- 
sciousness, during which they feed; whether they 
remain in a condition of partial torpor, with slow- 
ing of all the vital processes, and yet not in absolute 
insensibility and with cessation of respiration, etc. 
—all these questions seem to be as yet wholly un- 
decided. 
It has long been known that many cold-blooded 
animals hibernate and, under altered conditions, 
estivate; it is further beheved that among warm- 
blooded animals, besides bats, many rodents, and some 
allied animals hibernate. But when the matter is 
looked into carefully it is found that the term “ hiber- 
nation” has been used in a loose and very plastic sense 
by different authors. It is highly desirable, therefore, 
that writers should state exactly to what extent the 
animal they describe as “torpid,” “hibernating,” or 
“in winter-sleep,” deviates functionally from the 
normal; also, that the exact time of the observations 
be recorded. There is a certain amount of evidence 
that even birds, representing the highest type of 
activity, may possibly hibernate, and that many 
animals, not usually thus affected, may become so 
under exceptional circumstances — indeed that man 
himself, owing to peculiar states of the nervous system, 
may pass into a condition (“trance”) having much in 
common with the hibernation of lower animals. I 
think it is very probable that, when the matter has 
been fully investigated, all degrees of cessation of 
functional activity will be found represented, from the 
normal daily sleep of man and other animals to the 
lowest degree of activity consistent with the actual 
maintenance of life. The Flying Squirrel is nocturnal 
in habits and exceedingly active, even in confinement, 
as Prof. Perkins (Joc. cit.) has shown; but during the 
day-time it seems not to be correspondingly quick—in 
