IIIBKRXATION. l^ 



cases a wise provision , since the lean seasons of the year are 

 passed in safety, the difficulty of obtaining food in rigorous 

 weather being dispensed with. The lower animals generally 

 seem to possess a remarkable power of resisting cold and may 

 be reduced to a condition of apparent death, yet not identical 

 with the torpidity usually produced by low temperatures. It 

 is debatable whether in animals this torpidity arises more from 

 a question of escaping cold than from avoiding starvation. 

 But be that as it may, very many of the dwellers in field and 

 forest spend the Winter months in that deep and dreamless 

 sleep which breaks only with the genial warmth of Spring. 



Among the more familiar animals of our latitude which 

 hibernate during the colder months may be mentioned the 

 various species of bats, the chipmunk or " hackie," the mar- 

 mot or "groundhog," and some field mice. Frosty weather 

 in Autumn, or such as makes insects dormant, has the same 

 effect on all our bats in varying degrees. By that time they 

 have become excessively^ fat, and in this condition go into 

 hibernation in such places as are not subjected to \^xy low 

 Winter temperatures, preferably caves. From their retreats, 

 with the appearance of nocturnal insect life, they emerge in 

 Spring. Sometimes they come out during a February thaw, 

 and go back again until April. 



The following are the most nrarked peculiarities presented 

 by bats when in a state of perfect hibernation : — The respira- 

 tion is very nearly suspended, as is shown — First, By the 

 absence of all detectable respiration ; second. By the almost 

 entire absence of any change in the air of a bell jar or case in 

 which the animal is placed during the investigation ; third, 

 By the subsidence of the temperature to that of the atmos- 

 phere, and fourth. By the capability of supporting, for a 

 great length of time, the entire deprivation of air. The cir- 

 culation is reduced to an extreme degree of slowness. In an 

 observation made by Dr. Marshall Hall the heart of a bat was 

 found to beat but twenty-eight times in the minute. 



The chipmunk ( Tamias striata ) seeks its winter resting 



