insect creation. In studying its operations, as well as that of the beaver, and indeed of the other storing animals, we seem to get still deeper insight into the nature of that mysterious faculty, which, resembling reason in so many particulars, yet differs from it in this, that its impulses are uniform and unchangeable, belonging nearly in equal perfection in all ages, and under all circumstances, to every individual of the species; not capable of improvement by education, but regulated by propensities directed by a wisdom of which the species is not conscious, to the attainment of a future object, which they have not forethought to contemplate.* What is this but the impress of the finger of God? *Mr. Broderip gives a curious and interesting account of the habits of a tame beaver, brought to England, in 1825, which seems to illustrate the distinctive difference subsisting between reason and instinct, even where they appear to make the nearest approach. This little creature was still very young when let out of his cage, but immediately showed his building instinct. He began by selecting the longest materials within his reach, such as sticks, sweeping-brushes, &c., which he piled up in such a way that one end touched the wall, and the other projected into the room. "As the work grew high, he supported himself upon his tail, which propped him up admirably; and he would often, after laying on one of his building materials, sit up over against it, apparently to consider his work, or, as the country people say, 'judge it. This pause was sometimes followed by changing the position of the material judged,' and sometimes it was left in its place. After he had piled up his materials in one part of the room, (for he generally chose the same place,) he proceeded to wall up the space between the feet of a chest of drawers which stood at a little distance from it, high enough on its legs to make the bottom a roof for him, using for this purpose, dried turf and sticks, which he laid very even, and filling up the interstices with bits of coal, hay, cloth, or any thing he could pick up. This last place he seemed to appropriate for his dwelling; the former work seemed to be intended for a dam. When he had walled up the space between the feet of the chest of drawers, he proceeded to carry in sticks, cloth, hay, cotton, and to make a nest; and, when he had done, he would sit up under the drawers, and comb himself with the nails of his hind feet." It is scarcely necessary to say, that there was, in the case of this tame beaver, a propensity evinced to construct, where the object of the propensity no longer existed. The Author of its being, had bestowed on it this instinct, for the use of the species in its wild state; and, being destitute of the reasoning power which would have taught it the needlessness of the trouble it was taking, it still continued not only to build its house, and line its nest, where it was already sheltered and comfortable, but to construct a dam where there was no water. TENTH WEEK-WEDNESDAY. HYBERNATION.-TORPIDITY OF ANIMALS. AMONG the contrivances by which the Author of Nature enables the lower animals to sustain the privations of winter, that by which they are endowed with the faculty of becoming insensible to external objects, and of approaching a state of temporary death, is very worthy of attention. The ordinary phenomena of sleep have long been a subject of deep curiosity to the philosophical inquirer. The torpidity of animals during the cold season, in some respects, resembles this state; but there is a marked difference not only in the period of insensibility, and in the wise intentions of Providence which it fulfils, but also in the nature of this provision, as it affects the bodily frame, as well as in other particulars. The subject of torpidity has given rise to several ingenious experiments, by which some curious facts have been elicited. It is not our object to record these, but merely to give a succinct view of their results, in so far as they throw light on the operations of that Divine Being, from whose wisdom and goodness they derive their origin. The classes of animals, among whom this kind of hybernating principle is found, are very various, viz. quadrupeds, reptiles, insects, perhaps fishes, and, according to some, even birds. Among quadrupeds, the species which are known to become torpid, belong exclusively to the digitated order. A few of these species are of the class primates, such as the bat; and of the class feræ, such as the hedgehog; but the most numerous instances occur among the glires, of which the dormouse and the marmot are familiar examples. Attempts have been made, but without much success, to ascertain the causes on which torpidity depends. It is not extreme cold, as many have maintained, for some animals collect in deep caves, where the temperature is never low, or congregate and burrow in the earth, where the heat of their bodies preserves a temperature not much inferior to that of the average state of the external atmosphere; and others become lethargic even in warm climates. It is not the position which the body assumes, when about to become torpid, though this has also been alleged; for the different species seem to assume no other position than that to which they are accustomed in ordinary rest; it is not, so far as has been ascertained, any distinct and uniform state of the anatomical conformation, for anatomists have, in vain, attempted to establish any peculiarity in the bodily structure of such animals, which can account for the phenomenon; it is not, in fine, an immediate destitution of food, for a remarkable fact connected with this state is, that when animals become torpid, they are, generally speaking, unusually plump. and fat. Some of these circumstances, indeed, commonly occur at the period when these animals fall into the dormant state, and seem, in a certain degree, to influence the result. Thus, the exact time of the change may be hastened or retarded, by the temperature of the atmosphere, or the plenty or scarcity of food; but there seems to be no reason to conclude, that these circumstances, considered merely as physical causes, are sufficient to account for the phenomenon; and we are rather inclined to believe, that the animals themselves have some power in their own volition, of either inducing or resisting the lethargic condition. Spallanzani has seen bats in a torpid state, even during summer. A migratory hamster (cricetus glis,) was placed by Mangili in a state of confinement, in spring, when it was naturally in its waking period; and, as soon as it found that it could not escape, it refused to eat, and, throwing itself on its back, became torpid, in which state it remained till the 17th July. The land-testacea certainly have the power of becoming_torpid, independent of the severity of the weather. If specimens of the helix hortensis, [or garden snail,] for example, be placed, even a midsummer, in a box, without food, they soon attach themselves to the side of the place of their confinement, and become dormant; in which state they may be kept for several years. Torpidity, in short, is an instinct, and exhibits many of the interesting but mysterious characteristics of this faculty. When the season of storms and scarcity is about to arrive, the animals to whom this habit belongs, carefully select a proper place of retreat, respectively corresponding to their several natures, where they may spend, in a happy oblivion, the dreary winter months "The bat," to borrow the words of the article 'Hybernation,' in the Edinburgh Encyclopedia, "retires to the roof of gloomy caves, or to the old chimneys of uninhabited castles; the hedgehog wraps itself up in those leaves of which it composes its nest, and remains at the bottom of the hedge, or under covert of the furze which screened it during summer, from the scorching sun or the passing storm; the marmot and the hamster retire to their subterranean retreats, and when they feel the first approach of the torpid state, shut the passages to their habitations in such a manner, that it is more easy to dig up the earth any where else, than in the parts which they have thus fortified." "Many of those animals, particularly such as belong to the great natural family of gnawers, make provision in their retreats during the harvest month. The marmot, it is true, lays up no stock of provisions; but the hamsters fill their stores with all kinds of grain, on which they are supposed to feed until the cold becomes sufficiently intense to induce torpidity. The cricetus glis, or migratory hamster of Pallas, also lays up a stock of provisions. The same remark is equally applicable to the dormouse.” Animals, in preparing for this dormant state, are considerably actuated by their usual habits while awake, not only in the choice of a place of retreat, but also with regard to their social or solitary habits. Thus, the hedgehog and dormouse spend their period of insensibility alone, while the marmot, the hamster, and the bat, collect, for this purpose, in large societies. Some curious particulars have been noted of the phys ical condition of animals during their torpidity, which it seems unnecessary to do more than barely to enumerate. In this state, they suffer a great diminution of bodily temperature; they breathe slowly, and only at intervals proportioned to the depth of their slumber, sometimes with long periods of total intermission; the circulation of their blood becomes languid to such an extent, that even the pulsation of the heart is scarcely felt; the animal irritability decreases, so that limbs may be lopped off, and even the vital parts laid open, almost without exciting any symptoms of feeling; the action of the digestive organs is suspended; the body becomes gradually emaciated, and its weight is diminished, but without impairing the living principle, which, on the contrary, is found to be in a remarkably energetic and active state at the period of resuscitation. Many of the observations which we have made as to quadrupeds, will apply also to reptiles. These coldblooded animals adopt similar precautions in selecting proper places of retreat, to protect them from their enemies, and to preserve them from sudden alternations of temperature. Those, which inhabit the waters, sink into the soft mud; while such as live on land, enter the holes and crevices of rocks, or other places, where there is little change of temperature. Thus disposed of, they obey the impulse, and become torpid. The effect of cold in inducing and prolonging this state, is much more remarkable than in warm-blooded animals. It is said that frogs and snakes may be kept in a torpid state, in an icehouse, for several years, without any diminution of their vital energy. It is, perhaps, on a similar principle, that toads have been found alive, after having, for centuries, been imbedded in the heart of stones. The torpidity of the mollusca tribes,* and of insects, is much more general than that of the higher genera of animals; but as the state of these more minute animals during winter has occupied our attention in other papers, I shall at present pass the subject with this single obser * [Soft animals; such as cuttle-fish, shellfish, snails, &c.—Am. ED.] |