This sullen and forbidding-looking animal, the most ravenous and ferocious that infests the more temperate regions of the earth, of many parts of which he is the terror and the scourge, is distinguished from the humble, generous, and faithful friend of man, the domestic dog, by no very remarkable or striking character; and yet there is something in his physiognomy, gait, and habit, which is at once so peculiar and so repulsive, that it would be almost impossible to confound a Wolf, however tame, with the most savage and the most wolflike of dogs. For the separation of the two species, Linnæus, as we have seen in the preceding article, had recourse to the tail; and having determined that that of the dog was uniformly curved upwards, he attributed to that of the Wolf a completely opposite direction, that is to say, a curvature inwards; assigning, at the same time, a straight or a deflected position to those of all the other animals of the group. The deflected, or down-pointing, direction is, however, equally common in the Wolf with the incurved; and this petty distinction, which has little to do with structure, and still less with habits, is hardly deserving of serious attention. More obvious and more essential differences will be found in the cast of his countenance, which derives a peculiar expression from the obliquity of his eyes; in the breadth of his head, suddenly contracting into a slender and pointed muzzle; in the size and power of his teeth, which are comparatively greater than those of any dog of equal stature; in the stiffness and want of pliability of his limbs; in his uniformly straight and pointed ears; and in a black stripe which almost constantly, and in nearly every variety of the species, occupies the front of the fore leg of the adult. His fur, which differs considerably in texture and colour, from the influence of climate and of seasons, is commonly of a grayish yellow, the shades of which are variously intermingled; as he advances in age it becomes lighter, and in high northern latitudes frequently turns completely white, a change which also takes place in many other animals inhabiting the polar regions.