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 social ani mals, as the marmot, the hamster, and the bat, spend the period of their torpidity, as well as the ordinary 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 re treats, during the harvest months. The marmot, it is true, lays up no stock of food ; hut the hamsters fill their store house with all kinds of grain, on which they are supposed to feed, until the cold becomes sufficiently intense to in duce torpidity. The Criectus glis, or migratory hamster of Pallas, also lays up a stock of provision. And it is proba ble that this animal partakes of its stock of provisions, not only previous to torpidity, but also during the short inter vals of reviviscence, which it enjoys during the season of lethargy. The same remark is equally applicable to the dormouse.
Having thus made choice of situations w here they are protected from sudden alterations of temperature, and as sumed a position similar to that of their ordinary repose, they fall into that state of insensibility to external objects, which we are now to examine more minutely. In this tor pid state they suffer a diminution of temperature ; their respiration and circulation become languid ; their irritabili ty decreases in energy ; and they suffer a loss of weight. Let us now attend to each of these changes separately.
I. Diminished temperature. When we take in our hand any of these hybernating torpid animals, which we are now considering. they feel cold to the touch, at the same time that they are stiff, so that we are apt to conclude, without farther examination, that they are dead. This reduction of temperature is not the same in all torpid quadrupeds. It varies according to the species. Hunter, in his " 4 Obser vations on certain parts of the Animal Economy," informs us, on the authority of Jenner, that the temperature of a hedgehog at the diaphragm was 97° of Fahrenheit, in sum mer, when the thermometer in the shade stood at 78°.
Professor Mangili states the ordinary heat of the hedgehog a little lower, at 27° of Reaumur,or about 93° of Fahrenheit. In winter, according to fernier, 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 atmosphere was at 26°, the heat of the animal in the cavity of the abdomen, where an incision was made, was reduced so low as 30°. The same animal, when exposed to the cold atmosphere of for two days, had its heat at the rectum elevated to 93°, the wound in the abdomen be ing so much diminished in size as not to admit the ther mometer. At this time, however, it was lively and active, and the bed in which it lay felt warm. As this animal allow ed its heat to descend to when in its natural state of tor pidity, and when there was no necessity for action, the in creased temperature cannot be attributed to the cold, but to the wound, which called forth the powers of the animal to repair an injury, which reparation could not be effected at a temperature below the standard heat of the animal. • lime sources of error in making experiments where the liv" ing principle is concerned are so numerous, that attention ougM to be bestowed on every circumstance likely to influ ence the result.
The zizel, (4rctomys according to Pallas, usu ally possesses a summer temperature of 103° Fehr. hut during winter, and when torpid, the mercury rises only to 80° or 84°. The tempei attire of the dormouse (111yoxus muscardinus) during summer, and in its active and healthy state, is 101°. When rolled up and torpid during winter, the thermometer indicates 43°, 39°, and even 35°, on the external parts of the body. When introduced into the stomach, the temperature was found to be 67°, and some times Mangili found this animal torpid even when the temperature of the air was 66°. Hence he considers it as the most lethargic of animals.
The marmot (Arctomys marmota) possesses a summer temperature of 101° or 1020, which is gradually reduced in the torpid season to 43°, and even lower.