Of the loir, or great dormouse, or as some naturalists have termed it, the fat squirrel, there are three species; and, like the marmot, they all sleep during the winter; namely, the loir, the lerot, and the muscardin, or common dormouse. These three species have been confounded together although they are very different, and easily distinguished. The loir is nearly of the size of the squirrel, and like that animal, has its tail covered with long hair; the lerot is not so large as a rat, has very short hair on its tail, except at the extremity, where there is a tuft of long hair; the dormouse is not bigger than the common mouse, its tail is covered with longer hair than the lerot's, but shorter than the loir's, and it also has a tuft at the extremity. The loir differs from the other two, by having black spots about its eyes, and the dormouse by having white hair upon his back. They are all white or whitish under the neck and belly; the white of the lerot is beautiful, that of the loir more dark, and that of the dormouse has a yellow line in all the inferior parts. _Engraved for Barr's Buffon._ [Illustration: FIG. 87. _Scrotine Bat._] [Illustration: FIG. 88. _Horse-shoe Bat._] [Illustration: FIG. 89. _Barbastelle Bat._] [Illustration: FIG. 90. _Dormouse._] [Illustration: FIG. 91. _Alpine Marmot._] There is no truth in the assertion that these animals sleep during winter, for they are not in a state of natural sleep, but in a torpor produced by the coldness of the blood, by which they lose the use of their senses and members. Their internal heat does not exceed the temperature of the air. When the heat of the air is ten degrees above the freezing point, their heat is exactly the same. The ball of a small thermometer I have plunged into the bodies of several living lerots, and always found the heat of their bodies was nearly equal to the temperature of the air; and sometimes when applied to the very heart, I have observed the thermometer fall from half a degree to a whole one, the temperature of the air being at eleven. Now it is well known that the internal heat of man, and of the generality of quadrupeds, at all times exceeds thirty, and therefore there is little reason to be surprised that these animals, whose heat is so small, should become torpid, when their little internal heat ceases to be assisted by the external heat of the air; a circumstance that naturally happens when the thermometer is not above ten or eleven degrees above the freezing point. This is the real cause of the torpor of these animals, a cause which has been overlooked, although it extends to all animals which sleep during winter. Alike are its effects upon these animals, the hedge-hog and bats; and though I have never had the opportunity of trying them upon the marmot, I am persuaded its blood is not less cold, since like them it is subject to a torpor during winter.