From this enunciation of the primary fact in sleep, we may trace the whole of the pheno mena of this singular condition. In the state of activity, the cerebral system exerts a peculiar and continual influence over the true spinal, which ceases during sleep. In this manner the functions of the latter appear impaired ; the re spiration especially, and with the respiration the circulation, with which it always maintains a certain relation, becomes slower, irregular, and suspended at intervals. These phenomena observable in ordinary sleep are still more re markable in the deep sleep or lethargy of hibernation or diurnation.
In order that the effects of hibernation may be traced in relation to all the functions of the animal economy, I must enter into a few brief details relative to the arrangement of these functions and the order in which I propose to notice them. The most simple and natural arrangement of the functions appears to me to be the following :— I proceed to trace the influence of sleep, and of the deeper sleep of hibernation upon these various functions, beginning with the former.
I. Qf sleep.—It was first ascertained experi mentally by Messrs. Allen and Pepys, that the quantity of respiration is diminished in ordinary sleep.* The acts of respiration are obviously less frequent and less regular, being frequently suspended for a moment and renewed by a deep inspiration. The animal frame becomes more susceptible of the influence of cold. It is most probable that, during this condition, the irrita bility of the muscular system is augmented, and that this is one of the final objects of sleep; experiments, however, are still wanting to establish a fact in reference to ordinary sleep, which is clearly proved in regard to the sleep of hibernating animals, and the deeper sleep or lethargy of I shall now proceed to treat of the sleep of hibernating animals.
II. of the sleep of hibernating animals.—In the sleep of the hibernating animal, the respira tion is more or less impaired : if the animal be placed in circumstances which best admit of observation, the acts of respiration will be found to have greatly diminished ; if it be placed in the pneumatometer, little alteration is 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,t and the bat.: If other authors have riot 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 diurnal ion. 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 minutes 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 or The duration of this sleep is from two to three days, accord ing to the temperature of tire 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.