774 



HIBERNATION. 



If the hedgehog in a state of the most perfect 

 lethargy, uncomplicated with torpor, be touched, 

 its respiration is resumed, and it coils itself up 

 more forcibly than before. The dormouse, in 

 similar circumstances, unfolds itself; and the 

 bat moves variously. Not the slightest stiffness 

 is observed. The hedgehog, when roused, walks 

 about, and does not stagger, as has been asserted. 

 The bat speedily takes to the wing, and flies 

 about with great activity, although exhaustion 

 and death may subsequently result from the 

 experiment. The phenomena are similar to 

 those of awaking from natural sleep. Impaired 

 motility, stiffness, lameness, &c. belong to tor- 

 por, and not to true hibernation. 



III. Of reviviscence. Not the least inte- 

 resting of the phenomena connected with hiber- 

 nation are those of reviviscence. Hibernation 

 induces a state of irritability of the left side of 

 the heart, which, with high respiration and an 

 arterialized blood, would be incompatible with 

 life. Respiration suddenly restored, and per- 

 manently excited, is, therefore, as destructive as 

 its privation in other circumstances. 



All those bats which were sent to me from 

 distant parts of the country died. The conti- 

 nued excitement from the motion of the coach 

 keeping them in a state of respiration, the ani- 

 mal perished. One bat had, on its arrival, 

 been roused so as to fly about. Being left 

 quiet, it relapsed into a state of hibernation. 

 The excitement being again repeated the next 

 day, it again flew about the room ; on the suc- 

 ceeding day it was found dead. 



It is in accordance with this law, that we 

 observe hibernating animals adopting various 

 measures to secure themselves from frequent 

 sources of disturbance and excitement. They 

 choose sheltered situations, as caverns, burrows, 

 &c. secure from the rapid changes and the in- 

 clemencies of the weather and season. Many 

 form themselves nests ; others congregate toge- 

 ther. The hedgehog and the dormouse roll 

 themselves up into a ball. The common bat 

 suspends itself by the claws of its hinder feet, 

 with its head dependent, generally in clusters ; 

 the horseshoe bat (ferrum equinum) spreads its 

 wings so as to embrace and protect its fellows. 



All these circumstances are obviously de- 

 signed to prevent disturbed hibernation. 



In the depth of caverns, and other situations 

 sheltered from changes of temperature in the 

 atmosphere, the calls of hunger are probably 

 the principal cause of reviviscence in the spring. 

 The other causes of reviviscence are the return 

 of warmth and external excitements : it is inte- 

 resting to observe and trace the gradual return 

 of respiration in the former case, and of the 

 temperature of the animal in the latter. 



If the hibernating hedgehog be touched even 

 very gently, it draws a deep breath, and then 

 continues to breathe for a short time. If this 

 excitement be repeated, the animal is perma- 

 nently roused, and its temperature raised. If 

 the temperature of the atmosphere be augment- 

 ed, the respiration is gradually excited, and the 

 animal is gradually restored to its state of 

 activity. 



If a hibernating animal be excited in a very 



cold atmosphere, its temperature rises variously, 

 and then falls. A bat was perfectly lethargic 

 in a temperature of 36. A fine thermometer, 

 with a cylindrical bulb, was introduced into its 

 stomach; it rose to 39. One hour after- 

 wards, the animal not being further disturbed, 

 the respiration was rapid, and the temperature 

 in the stomach 93. Shortly afterwards the 

 temperature was 90. The minute circulation 

 was pretty good, and pulsatory in the arteries, 

 the heart beating from twenty-eight to thirty- 

 six times in the minute. 



In another bat, in an atmosphere of the tem- 

 perature of 36, the thermometer in the stomach 

 rose to 39. The animal being continually ex- 

 cited, the temperature rose to 65, but speedily 

 fell to 60. 



The animal excited and revived in this man- 

 ner is in a state of exhaustion and inanition. It 

 is incapable of maintaining its temperature if 

 exposed to cold, and will die unless it repass 

 into the state of hibernation. It may be com- 

 pared to the case of the mouse deprived of food 

 in the following experiment of Mr. Hunter. 

 " A mouse was put into a cold atmosphere of 

 13 for an hour, and then the thermometer was 

 introduced as before ; but the animal had lost 

 heat, for the quicksilver at the diaphragm was 

 carried only to 83, in the pelvis to 78. 



" In order to determine whether an animal 

 that is awakened has the same powers, with 

 respect to preserving heat and cold, as one that 

 is vigorous and strong, I weakened a mouse by 

 fasting, and then introduced the bulb of the 

 thermometer into its belly ; the bulb being at 

 the diaphragm, the quicksilver rose to 97 ; in 

 the pelvis to 95, being two degrees colder than 

 the strong mouse : the mouse being put into 

 an atmosphere as cold as the other, and the 

 thermometer again introduced, the quicksilver 

 stood at 79 at the diaphragm, and at 74 in 

 the pelvis. 



" In this experiment the heat at the dia- 

 phragm was diminished 18, in the pelvis 21. 



" This greater diminution of heat in the 

 second than in the first, we may suppose pro- 

 portional to the decreased power of the animal, 

 arising from want of food.' * 



But extreme cold alone, by a painful effect 

 induced on the sentient nerves, rouses the 

 hibernating animal from its lethargy, as has 

 been remarked already, and is illustrated by the 

 following experiments of Hunter. " Having 

 brought a healthy dormouse, which had been 

 asleep from the coldness of the atmosphere, 

 into a room in which there was a fire, (the 

 atmosphere at 64,) I introduced the thermo- 

 meter into its belly, nearly at the middle, be- 

 tween the thorax and pubis, and the quicksilver 

 rose to 74 or 75 ; turning the bulb towards 

 the diaphragm, it rose to 80 ; and when I ap- 

 plied it to the liver, it rose to 81 . 



" The mouse being placed in an atmosphere 

 at 20, and left there half an hour, when taken 

 out was very lively, even much more so than 

 when put in. Introducing the thermometer 

 into the lower part of the belly, the quicksilver 



* Animal (Economy, pp. 114, 115. 



