DRUPEDS.
The quadrupeds which are known to become torpid be long exclusively to the digitated order. Some species are found among the primates, as the different kinds of bats ; among the ferce we find the hedgehog and the tanric ; while among the glires the torpid species are numerous, and their habits have been studied with the greatest atten tion, as the marmot, the hamster, and the dormouse.
Thefood of these animals is very different. according to the orders or genera to which they belong. The bats sup port themselves by catching insects, and those chiefly of the lepidopterous kinds; the hedgehog lives on worms and snails ; while others, as the marmot and hamster, feed on roots, seeds, and herbs.
It is usually supposed that torpid animals are confined to 'the cold regions of the earth. That they abound in such regions, roust be admitted ; but their range of latitude is not so limited as to prevent their occurrence even in warm countries. Thus the Dipus sagitta, which is found from the 53d degree of north latitude to the tropics, is equally torpid during the winter months in Egypt as in Siberia. In the former country it is more easily revived by a very slight increase of temperature, its lethargy not being so profound. The Tanric (Tanric caudatus,) which is an in habitant of India and Madagascar, becomes torpid even in those countries, and continues so during nearly six months of the year.
The precise period of the year in which these animals re tire to their winter quarters and become torpid, has not been ascertained with any degree of precision. The jump ing mouse of Canada (Gerbillus Canadensis) is said to retire to its torpid state in September, and is again restored to ac tivity in the month of May. The torpid animals of this country usually retire in October, and reappear in April. It appears probable, however, that the different species do not'all retire at the same time, but, like the migrating birds, perform their movements at separate periods. It is also probable that the time of retirement of each species varies according to the mildness or severity of the season. In ge neral, however, they retire from active life when their food has become difficult to obtain, when the insects have fled to their hiding places, and the cold has frozen in the ground the roots and the seeds on which they subsist At the pe riod of their reviviscence, the insects are again sporting in the air, and the powers of vegetable life are exerted in the various processes of germination and vegetation. In short, during the dead season of vegetable life, these animals pass their time in this lethargic state. We see the coincidence, but we cannot well account for the connection.
Previous to their entrance into this state of lethargy, these animals select a proper place, in general assume a particular position, and even in some cases provide a small stock of food.
All these torpid animals retire to a place of safety, where, at a distance from their enemises, and protected as much as possible from the vicissitudes of temperature, they may sleep out, undisturbed, the destined period of their slum bers. The bat retires to the roof of gloomy caves, or to the old chimnies of uninhabited castles. The hedge-hog wraps itself up in those leaves of which it composes its nest, and remains at the bottom of the hedge, or under the covert of the furze, which screened it, during sum mer, from the scorching sun or the passing storm. The
marmot and the hamster retire to their subterranean re treats, and when they feel the first approach of the tor pid state, shut the passages to their habitations in such a that it is more easy to dig up the earth any where else, than in such parts which they have thus fortified. The jumping mouce of Canada seems to prepare itself for its torpidity in a very curious manner, as we are in formed by Major-General Davies, in the Linnean Transac tions, vol. iv. p. 156, on the authority of a labourer. A spe cimen w hich was found in digging the foundation for a summer-house'in a gentleman's garden about two miles from Quebec, in the latter end of May 1787, was " en closed in a ball of clay, about the size of a cricket ball, near ly an inch in thickness, perfectly smooth within, and about twenty inches, under ground. The man who first discover ed it, not knowing what it was, struck the ball with his spade, by which means it was broken to pieces, or the ball also would have been presented to me." Much stress has been laid upon the position which these animals assume, previous to their becoming torpid, on the supposition that it contributes materially to produce the lethargy. In describing this position, Dr Reeves (in his Essay en the Toi pidity of Animals) observes, " that this tribe of quadrupeds have the habit of rolling themselves into the form of a ball during ordinary sleep ; and they inva riably assume the same attitude when in the torpid state, so as to expose the least possible surface to the action of cold: the limbs are all folded into the hollow made by the bend ing of the body ; the clavicles and the sternum are pressed against the fore part of the neck, so as to interrupt the flow of blood which supplies the• head, and to compress the trachea : the abdominal viscera and the hinder limbs are pushed against the diaphragm, so as to interrupt its mo tions, and to impede the flow of blood through the large vessels which penetrate it, and the longitudinal extension of the cavity of the thorax is entirely obstructed. Thus a confined circulation is carried on through the heart, pro bably adapted to the last weak actions of life, and to its gra dual recommencement." Professor Mangili of Pavia, (?n wales du Museum, torn. ix.) with greater simplicity of lan guage, says, that the marmot rolls itself up like a ball, hav ing the nose applied contrary to the anus, with the teeth and eyes closed. He also informs us, that the hedge-hog, when in a torpid state, in general reposes on the right side. The bat, however, during the period of its slumbers, prefers a very differentposture. It suspends itself from the ceiling °Nile cave to which it retires, by means of its claws, and in this attitude outlives the winter. This is the natural po sition of the bat when at rest, or in its ordinary sleep. In short, little more can be said of the positions of all these torpid animals, than the currespondclice with those which they assume during the periods of their ordinary repose.