One of the most striking proofs of the influence of climate on the form and character of this animal, occurs in the bull-dog. When transported to India he becomes, in a few years, greatly altered in form, loses all his former courage and ferocity, and becomes a perfect coward.
It is probable that all dogs sprang from one common source, but climate, food, and cross-breeding caused variations of form, which suggested particular uses; and these being either designedly or accidentally perpetuated, the various breeds of dogs thus arose, and they have become numerous in proportion to the progress of civilization. Among the ruder, or savage tribes, they possess but one form; but the ingenuity of man has devised many inventions to increase his comforts: he has varied and multiplied the characters and kinds of domestic animals for the same purpose, and hence the various breeds of horses, and cattle, and dogs.
The parent stock it is now impossible to trace; but the wild dog, wherever found on the continent of Asia, or Northern Europe, has nearly the same character, and bears no inconsiderable resemblance to the British fox-dog, while many of those from the Southern Ocean can scarcely be distinguished from the English lurcher. There is, however, no more difficulty in this respect with regard to the dog, than any other of our domesticated animals. Climate, or chance, produced a change in certain individuals, and the sagacity of man, or, perhaps, mere chance, founded on these accidental varieties numerous breeds possessed of certain distinct characteristic properties. The degeneracy of the dog, also, in different countries, cannot for a moment be disputed.
The most natural arrangement of all the varieties of the dog is according to the development of the frontal sinus and the cerebral cavity, or, in other words, the power of scent, and the degree of intelligence. This classification originated with M.F. Cuvier, and has been adopted by most naturalists. He reckoned three divisions of the dog:
I. Those having the head more or less elongated, and the parietal bones of the skull widest at the base, and gradually approaching towards each other as they ascend, the condyls of the lower jaw being on the same line with the upper molar teeth. The _Greyhound_ and all its varieties belong to this class.