396 



HYBERNATION. 



Animals 

 which 

 become 

 Torpid. 



pid 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 mild- 

 ness or severity of the season. In general, 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 lias frozen in the ground 

 the roots and the seeds on which they subsist. At the 

 period of their reviviscence, the insects are again sport- 

 ing in the air, and the powers of vegetable life are ex- 

 erted in the various processes of germination and vege- 

 tation. 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 enemies, and protect- 

 ed as much as possible from the vicissitudes of tempe- 

 rature, they may sleep out, undisturbed, the destined 

 period of their slumbers. 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 bot- 

 tom of the hedge, or under the covert of the furze, 

 which screened it, during summer, from the scorching 

 sun or the passing storm. The marmot and the ham- 

 Bter 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 

 jt is more easy to dig up the earth any where else, 

 than in such parts which they have thus fortified. 

 The jumping mouse of Canada seems to prepare itself 

 for its winter torpidity in a very curious manner, as we 

 are informed by Major-General Davies, in the Linnean 

 Transact ions, vol. iv. p. 156, on the authority of a la- 

 bourer. A specimen which 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 

 17S7, was " enclosed in a ball of clay, about the size of a 

 cricket ball, nearly an inch in thickness, perfectly 

 smooth within, and about twenty inches under ground. 

 The man who first discovered 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 tor- 

 pid, on the supposition that it contributes materially to 

 produce the lethargy. In describing this position, Dr 

 Reeves (in his Essay on the Torpidity of Animals) ob- 

 serves, "that this tribe of quadrupeds have the habit of 

 rolling themselves into the form of a ball during ordi- 

 nary sleep ; and they invariably assume the same at- 

 titude 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 bending 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 inter- 

 rupt its motions, and to impede the flow of blood, 



Animali 

 which 

 bec "'e 



through the large vessels which penetrate it, and the 

 longitudinal extension of the cavity of the thorax is en- 

 tirely obstructed. Thus a confined circulation is car- 

 ried on through the heart, probably adapted to the last 

 weak actions of life, and to its gradual recommence- 

 ment." Professor Mangili of Pavia, (Annales du Mu- 

 seum, torn. ix. ) with greater simplicity of language, 

 says, that the marmot rolls itself up like a ball, having 

 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 ofita 

 slumbers, prefers a very different posture. It suspends 

 itself from the ceiling of the cave to which it retires, 

 by means of its claws, and in this attitude outlives the 

 winter. This is the natural position 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 animais. 

 than the correspondence with those which they assume 

 during the periods of their ordinary repose. 



It is also observable, that those animals which are of 

 solitary habits during the summer season, as the hedge- 

 hog and dormouse, are also solitary during the period 

 of their winter torpidity; while the congregating so- 

 cial animals, as the marmot, the hamster, and the bat, 

 spend the period of their torpidity, as well as the ordi- 

 nary terms of repose, collected together in families or 

 groups. 



Many of those animals, particularly such as belong 

 to the great natural family of gnawers, make provision 

 in their retreats, during the harvest months. The mar- 

 mot, it is true, lays up no stock of food ; but the ham- 

 sters fill their storehouse with all kinds of grain, on 

 which they are supposed to feed, until the cold be- 

 comes sufficiently intense to induce torpidity. The 

 Cricetus glis, or migratory hamster of Pallas, also lays 

 up a stock of provision. And it is probable that this 

 animal partakes of its stock of provisions, not only pre- 

 vious to torpidity, but also during the short intervals 

 of reviviscence, which it enjoys during the season of le- 

 thargy. The same remark is equally applicable to the 

 dormouse. 



Having thus made choice of situations where they 

 are protected from sudden alternations of temperature, w hidftor- 

 and assumed a position similar to that of their ordinary pid animals 

 repose, they fall into that stale of insensibility to external undergo. 

 objects which .we are now to examine more minutely. 

 In this torpid state they suffer a diminution of tempe- 

 rature; their respiration and circulation become lan- 

 guid ; their irritability decreases in energy ; and they 

 suffer a loss of weight. Let us now attend to. each of 

 these changes separately. 



1. Diminished temperature. When we take in our Diminithec 

 hand any of these hybemating torpid animals, which tempera- 

 we are now considering, they feel cold to the touch, at ture ' 

 the same time that they are stiff, so that we are apt to 

 conclude, withoutfarther examination, that they aredead. 

 Thisreduction of temperature is notthe same in all torpid 

 quadrupeds. It varies according to the species. Hunter, 

 in his " Observations on certain parts of the Animal Eco- 

 nomy," informs us, on the authority of Jenner, that the 

 temperature of a hedgehog at the diaphragm was 97 of 

 Fahrenheit, in summer, when the thermometer in the 

 shade stood at 78. Professor Mangili states the ordi- 

 nary heat of the hedgehog a little lower, at 27 of lieu- 

 mur, or about 93 of Fahrenheit, In winter, according 

 to Jenner, the temperature of the air being 44, and 

 the animal torpid, the heat in the pelvis was 45, and 

 at the diaphragm 48^. When the temperature of the 



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