HIBERNATION. 



767 



induced in the bulk of the air; if its tempera- 

 ture be taken by the thermometer, it will be 

 found to be many degrees lower than that of 

 the animal in its active state; if it be deprived 

 of atmospheric air, it is not immediately in- 

 commoded or injured. 



These facts I have observed in the hedge- 

 hog,* the dormouse,f and the bat.J If other 

 authors have not made the same observations, 

 it is because they have not been aware how 

 easily this sleep is disturbed. To walk over 

 the floor, to touch the table, is sufficient, in 

 many instances, to rouse the animal, to re-pro- 

 duce respiration, and to frustrate the experi- 

 ment. 



The bat, which is a crepuscular or nocturnal 

 feeder, regularly passes from its state of activity 

 to one which may be designated diurnation. 

 The respiration and the temperature fail; the 

 necessity for respiration is greatly lessened. 



During the summer of 1831, I carefully ob- 

 served a bat in this condition. If it were quite 

 quiet, its respiration became very imperfect; 

 its temperature was but a few degrees above 

 that of the atmosphere; being placed under 

 water, it remained during eleven mimites unin- 

 jured, and on being removed became lively 

 and continued well. 



I have more recently watched the habits of 

 two hedgehogs, in a temperature varying from 

 45 to 50. These animals alternately awake, 

 take food, and fall asleep. One of them is 

 frequently awake, whilst the other is dormant, 

 and goes to sleep at a time that the other 

 awakes, but without regularity. When awake, 

 the temperature of each, taken by pressing the 

 bulb of a thermometer upon the stomach, is 

 about 95; when dormant, it is 4.5; that of 

 the atmosphere being 42 or 43. The duration 

 of this sleep is from two to three days, accord- 

 ing to the temperature of the atmosphere. On 

 the 4th of February, 1832, the temperature of 

 the atmosphere being 50, both the hedgehogs 

 were dormant, the temperature of one was 

 51, and that of the other 52; on the succeed- 

 ing day, the temperature of the atmosphere had 

 fallen one degree, the temperature of one of the 

 hedgehogs was 49, whilst that of the other, 

 which had become lively, had risen to 87; on 

 the succeeding day, the first had become some- 

 what lively, and its temperature had risen to 

 60, that of the other being 85, and that of the 

 atmosphere 47. 



I have observed precisely the same alterna- 

 tions in the dormouse ; except that this animal 

 awakes daily in moderate temperatures, takes 

 its food, and re-passes into a state of sleep, in 

 which the respiration is greatly impeded, and 

 the temperature little higher than that of the 

 atmosphere. 



On the day on which the observations were 

 made on the hedgehogs, the atmosphere being 

 49, that of two dormice was 52 ; on the suc- 

 ceeding day, the external temperature being 

 47, that is, lower by two degrees, the tempera- 



* Erinaceus Europaens. 

 t Mvoxus avellanarius. 

 Vespertilio noctula. 



ture of one of these dormice was 92, and that 

 of the other 94; and only three hours after- 

 wards, the temperatures were 60 and 70 re- 

 spectively, with a slight appearance of lethargy. 

 The hedgehog and the dormouse appear, in 

 fact, to awake from the call of hunger, then to 

 eat, and then again to become dormant, in 

 temperatures which may be termed moderate. 

 The bat, which could not find food if it did 

 awake, does not undergo these periodical 

 changes, except in the summer season. It ap- 

 pears to me, from the most careful observation, 

 that there is every degree between the ordinary 

 sleep of these animals and the most profound 

 hibernation. 



It is quite obvious, from these observations, 

 that the ordinary sleep of hibernating animals 

 differs from that of others, by inducing a more 

 impaired state of the respiration and of the 

 evolution of heat, with an augmented power of 

 bearing the abstraction of the atmospheric air. 

 This sleep probably passes into true hiberna- 

 tion, as the blood which circulates through the 

 brain becomes more and more venous, from 

 the diminution of the respiration, and as the 

 muscular fibre of the heart acquires increased 

 irritability. 



It is absolutely necessary, in comparing the 

 powers of hibernating and other animals, of 

 evolving heat, accurately to observe whether 

 there be any tendency to sleep. Mr. Hunter's 

 and M. Ed wards 's experiments are deficient 

 for want of this attention. Mr. Hunter, com- 

 paring the common mouse and the dormouse, 

 exposed to a very low temperature, observes, 

 that the temperature of the former was " dimi- 

 nished 16 at the diaphragm, and 18 in the 

 pelvis ; while in the dormouse it gained five 

 degrees, but lost on a repetition." * The ex- 

 planation of these facts is afforded by the obser- 

 vation, that when the dormouse increased in 

 temperature it was " very lively," but that on 

 the " repetition" it had become " less lively ;" 

 the mouse was probably in a state of languor 

 from apprehension or for want of food. 



M. Edwards omits to mention whether the 

 hibernating animals, in his experiments, were 

 disposed to be lively or dormant, or whether 

 they had recently recovered from the dormant 

 state. He does not even mention whether the 

 experiments on the bat were performed in the 

 evening, its period of activity, or in the morn- 

 ing or day, its period of lethargy or diurnation. 

 Without a particular attention to these points, 

 no correct result could be obtained. The hiber- 

 nating animal, in a state of vigour and activity, 

 is a totally different being from the same animal 

 disposed to become dormant. 



In order to perform this experiment in a 

 satisfactory manner, the bat, for example, 

 should be employed in the evening, when it 

 has naturally awoke from its deep day-slumber, 

 the hedgehog when it has awoke spontaneously 

 to take food ; otherwise the disposition to sleep 

 may explain the loss of temperature. We must 

 hesitate, therefore, in subscribing to the follow- 

 ing conclusion of M. Edwards: " Nous voyons 



* Animal (Economy, p. 114. 



