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 (lay, the ememal temperature being that is, lower by two degrees, the tempera ture of one of these dormiee 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 filet, 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. I t 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 tire 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 AI. Edwards's experiments are deficient for want of this attention. Dir. Hunter, corn 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 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.
NI. 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 slate. lie 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 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 NI. Edwards: " Nous voyons que les chauves-souris produisent habituclle ment morns de chalcur que les animaux ii sang chaud, et que c'est priucipalement a cette cause qu'il faut attribuer l'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 animus it sang chaud, on y apercoit un rap port remarquable ; ils ne produisent pas assez de chaleur pour soutenir une temperature elevee, lorsque l'air est a un degre voisin de zero. Mais it y a cette difference, que c'est un etat passager chez les jeunes animaux it sang chaud, et qu'il est permanent chez les chauves souris.
Il est evident que les wares mammiferes hibernans doivent participer plus ou mains de cette maniere d'etre. Les faits que j'ai exposes sutlisent 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 it sang chaud, fls 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, it faut cependant l'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 wakefulness 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.