768 



HIBERNATION. 



que les chauves-souris produisent habituelle- 

 ment moins de chaleur que les animaux a sang 

 chaud, et que c'est principalement a cette cause 

 qu'il faut attribuer 1'abaissement de leur tempe- 

 rature pendant la saison froide. En comparant 

 cette experience sur la chauve-souris adulte 

 avec celles que nous avons faites sur les jeunes 

 animaux a sang chaud, on y apercoit un rap- 

 port remarquable ; ils ne produisent pas assez 

 de chaleur pour soutenir une temperature elevee, 

 lorsque 1'air est a un degre voisin de zero. 

 Mais il y a cette difference, que c'est un 

 etat passager chez les jeunes animaux a sang 

 chaud, et qu'il est permanent chez les chauves- 

 souris. 



" II est evident que les autres mammiferes 

 hibernans doivent participer plus ou moins de 

 cette rnaniere d'etre. Les fails que j'ai exposes 

 suffisent pour nous faire considerer ce groupe 

 d'animaux sous le point de vue suivant ; qu'au 

 printemps et en etc, dans leur etat d'activite et 

 de veille, lorsque leur temperature est assez 

 Elevee pour ne pas differer essentiellement de 

 celle qui caracterise les animaux a sang chaud, 

 ils n'ont pas la faculte de produire autant de 

 chaleur; et tout en admettant que d'autres 

 causes peuvent influer sur leur refroidissement 

 pendant leur hibernation, il faut cependant 

 1 'attribuer en grande partie a cette particularite 

 de leur constitution." * 



There are, in fact, these differences between 

 the young and the hibernating animal: 1. the 

 former cannot, when exposed alone to severe 

 cold, maintain its own temperature ; if the lat- 

 ter appears to be in the same case, it is only 

 because it has become affected with its peculiar 

 lethargy ; in its state of wakefulnes>s and activity 

 it maintains its usual elevated temperature in 

 the same manner as other adult animals ; 2. the 

 young animal, in losing its temperature, be- 

 comes affected, not, like the hibernating animal, 

 with lethargy, but with torpor, a totally diffe- 

 rent and a pathological condition which gene- 

 rally proves fatal. I must conclude these re- 

 marks by observing that I think the eminent 

 physiologist whom I have quoted has assimi- 

 lated the condition of the very young animal 

 and the adult hibernating animal erroneously. 

 The mere phenomenon of loss of temperature 

 is the same ; but the rationale of this pheno- 

 menon, its causes and its effects, are totally 

 different. 



III. Of perfect hibernation. I now proceed 

 to treat of perfect hibernation, of its causes, and 

 of its effects on the various functions which I 

 have enumerated. My observations will con- 

 sist principally of a detail of a series of obser- 

 vations and experiments made in the course of 

 the year 1831-1832, compared with the results 

 obtained by other inquirers. 



I consider that there is one special cause of 

 hibernation, that law imposed by the Creator, 

 according to which all animals become affected 

 with sleep at some period of each revolving 

 day, and the hibernating animal at some period 

 of the revolving year. We have thus presented 

 to us the phenomena of diurnal and nocturnal 



* Des A gens Physiques, p. 155. 



animals, and the winter-sleep and the summer- 

 sleep of hibernating animals. 



Exposure to cold, not too severe, disposes to 

 hibernation, as it disposes to ordinary sleep. 

 Severe cold, on the contrary, first rouses the 

 hibernating animal from its lethargy, and then 

 plunges this and all animals into a state of fatal 

 torpor. 



The absence of every kind of stimulus or ex- 

 citant, and a somewhat confined atmosphere,* 

 also conduce to hibernation. 



Every excitement, on the contrary, that of 

 hunger, that of the sexes probably, tend to dis- 

 turb this peculiar lethargy. It is in this man- 

 ner that we explain the periodicity of sleep and 

 hibernation, though there is probably also some 

 hidden influence of the seasons, of the day or 

 of the year, influences which have been traced 

 by Dr. Prout and by M. Edwards in regard 

 to the quantity of respiration. 



I now proceed to treat of the condition of the 

 several functions in hibernation. 



The process of sanguification is, in some 

 hibernating animals, nearly arrested ; in others, 

 it is entirely so. 



There is much difference in the powers of 

 digestion, and in the fact of omitting to take 

 food, in the hibernation of different animals. 

 The bat, being insectivorous, would awake in 

 vain ; no food could be found : the hedgehog 

 might obtain snails or worms, if the ground 

 were not very hard from frost : the dormouse 

 would find less difficulty in meeting with grain 

 and fruits. We accordingly observe a remark- 

 able difference in the habits of awaking from 

 their lethargy or hibernation, in these different 

 animals. 



I have observed no disposition to awake at all 

 in the bat, except from external warmth or excite- 

 ment. If the temperature be about 40 or 45, 

 the hedgehog, on the other hand, awakes, after 

 various intervals of two, three, or four days 

 passed in lethargy, to take food ; and again re- 

 turns to its state of hibernation. The dor- 

 mouse, under similar circumstances, awakes 

 daily. 



Proportionate to the disposition to awake 

 and take food, is the state of the functions of 

 the stomach, bowels and kidneys. The dor- 

 mouse and the hedgehog pass the faeces and 

 urine in abundance during their intervals of 

 activity. The bat is scarcely observed to have 

 any excretions during its continued lethargy. 



In the dormouse and the hedgehog, the sense 

 of hunger appears to rouse the animal from its 

 hibernation, whilst the food taken conduces to 

 a return of the state of lethargy. It has already 

 been observed, that there are alternations be- 

 tween activity and lethargy in this animal, with 

 the taking of food, in temperatures about 40 

 or 45. Nevertheless, abstinence doubtless con- 

 duces to hibernation, by rendering the system 



* M. de Saissy observes, " la marmotte, que j'ai 

 engourdie par deux fois differentes, ne Pa etc, je 

 crois, que parceque je me suis avise, quand la re- 

 spiration a ete bien affaiblie, de boucher le trou du 

 couvercle. Ce n'a ete que de cette maniere que je 

 suis parvenu a 1'engourdir ; car toutes les tentative 

 que j'avais faites avant ont etc vaines." 



