A third separation, however, seemed to be too much for this faithful animal's temper. He became gloomy, desponding, refused his food, and for a long time his life appeared in great danger. His health at last returned, but he no longer suffered the caresses of any but his keepers, and towards strangers manifested the original savageness of his species.

Mr. Bell, in his "History of Quadrupeds," mentions a curious fact, which, I think, still more strongly proves the alliance of the dog with the wolf, and is indeed exactly similar to what is frequently done by dogs when in a state of domestication. He informs us, that he "remembers a bitch-wolf at the Zoological Gardens, which would always come to the front bars of her den to be caressed as soon as he, or any other person whom she knew, approached. When she had pups, she used to bring them in her mouth to be noticed; and so eager, in fact, was she that her little ones should share with her in the notice of her friends, that she killed all of them in succession by rubbing them against the bars of her den, as she brought them forwards to be fondled."

Other instances might be mentioned of the strong attachment felt by wolves to those who have treated them kindly, but I will now introduce some remarks on the anatomical affinities between the dog, the fox, and the wolf, which serve to prove that the dog is of a breed distinct from either of the last-mentioned animals.

It must, in fact, be always an interesting matter of inquiry respecting the descent of an animal so faithful to man, and so exclusively his associate and his friend, as the dog. Accordingly, this question has been entertained ever since Natural History took the rank of a science. But the origin of the dog is lost in antiquity. We find him occupying a place in the earliest pagan worship; his name has been given to one of the first-mentioned stars of the heavens, and his effigy may be seen in some of the most ancient works of art. Pliny was of opinion that there was no domestic animal without its unsubdued counterpart, and dogs are known to exist absolutely wild in various parts of the old and new world. The Dingo of New Holland, a magnificent animal of this kind, has been shown to be susceptible of mutual attachment in a singular degree, though none of the experiments yet made have proved that he is capable, like the domestic dog, of a similar attachment to man. The parentage of the wild dogs has been assigned to the tame species, strayed from the dominion of their masters. This, however, still remains a question, and there is reason to believe that the wild dog is just as much a native of the wilderness as the lion or tiger. If there be these doubts about an animal left for centuries in a state of nature, how can we expect to unravel the difficulties accumulated by ages of domestication? Who knows for a certainty the true prototype of the goat, the sheep, or the ox? To the unscientific reader such questions might appear idle, as having been settled from time immemorial; yet they have never been finally disposed of. The difficulty, as with the dog, may be connected with modifications of form and colour, resulting from the long-continued interference of man with the breed and habits of animals subjected to his sway.

Buffon was very eloquent in behalf of the claim of the sheep-dog to be considered as the true ancestor of all the other varieties. Mr. Hunter would award this distinction to the wolf; supposing also that the jackal is the same animal a step further advanced towards civilization, or perhaps the dog returned to its wild state. As the affinity between wolf, jackal, fox, and dog, cannot fail to attract the notice of the most superficial observer; so he may ask if they do not all really belong to one species, modified by varieties of climate, food, and education? If answered in the negative, he would want to know what constitutes a species, little thinking that this question, apparently so simple, involves one of the nicest problems in natural history. Difference of form will scarcely avail us here, for the pug, greyhound, and spaniel, are wider apart in this respect, than many dogs and the wild animals just named. It has often been said that these varieties in the dog have arisen from artificial habits and breeding through a long succession of years. This seems very like mere conjecture. Can the greyhound be trained to the pointer's scent or the spaniel to the bulldog's ferocity? But admitting the causes assigned to be adequate to the effects, then the forms would be temporary, and those of a permanent kind only would serve our purpose. Of this nature is the shape of the pupil of the eye, which may be noticed somewhat particularly, not merely to make it plain to those who have never thought on the subject, but with the hope of leading them to reflections on this wondrous inlet to half our knowledge, the more especially as the part in question may be examined by any one in his own person by the help of a looking-glass. In the front of the eye then, just behind the transparent surface, there is a sort of curtain called the iris, about the middle of which is a round hole. This is the pupil, and you will observe that it contracts in a strong light, and dilates in a weaker one, the object of which is to regulate the quantity of light admitted into the eye. Now the figure of the pupil is not the same in all animals. In the horse it is oval; in the wolf, jackal, and dog, it is round, like our own, however contracted; but in the fox, as in the cat, the pupil contracts vertically into an elongated figure, like the section of a lens, and even to a sort of slit, if the light be very strong.

This is a permanent character, not affected, as far as is at present known, by any artificial or natural circumstances to which the dog has been subjected. Naturalists, therefore, have seized upon this character as the ground for a division of animals of the dog kind, the great genus Canis of Linnaeus, into two groups, the diurnal and nocturnal; not to imply that these habits necessarily belong to all the individuals composing either of these divisions, for that would be untrue, but simply that the figure of the pupils corresponds with that frequently distinguishing day-roaming animals from those that prowl only by night. It is remarkable that a more certain and serviceable specific distinction is thus afforded by a little anatomical point, than by any of the more obvious circumstances of form, size, or colour. Whether future researches into the minute structure of animals may not discover other means to assist the naturalist in distinguishing nearly allied species, is a most important subject for inquiry, which cannot be entertained here. But to encourage those who may be disposed to undertake it, I must mention the curious fact, that the group to which the camel belongs is not more certainly indicated by his grotesque and singular figure than by the form of the red particles which circulate in his blood. And here again the inherent interest of the matter will lead me to enter a little into particulars, which may engage any one who has a good microscope in a most instructive course of observations, not the least recommendation of which is, that a just and pleasing source of recreation may be thus pursued by evening parties in the drawing-room, since the slightest prick of the finger will furnish blood enough for a microscopic entertainment, and you may readily procure a little more for comparison from any animal.

Now the redness of the blood is owing to myriads of minute objects in which the colour of the vital fluid resides. They were formerly called globules, but as they are now known to be flattened and disc-like, they are more properly termed particles or corpuscles. Their form is wonderfully regular, and so is their size within certain limits; in birds, reptiles, or fishes, the corpuscles are oval. They are circular in man, and all other mammalia, except in the camel tribe, in which the corpuscles are oval, though much smaller than in the lower animals. Thus, in the minutest drop of blood, any one of the camel family can be surely distinguished from all other animals, even from its allies among the ruminants; and what is more to our purpose, in pursuing this inquiry, Mr. Gulliver has found that the blood-corpuscles of the dog and wolf agree exactly, while those of all the true foxes are slightly though distinctly smaller.

These curious facts are all fully detailed in Mr. Gulliver's Appendix to the English version of Gerber's Anatomy, but I think that they are now for the first time enlisted into the service of Natural History.

Thus we dismiss the fox as an alien to the dog, or, at all events, as a distinct species. Then comes the claim of the wolf as the true original of the dog. Before considering this, let us revert to the question of what constitutes a species. Mr. Hunter was of opinion that it is the power of breeding together and of continuing the breed with each other; that this is partially the case between the dog and the wolf is certain, for Lord Clanbrassil and Lord Pembroke proved the fact beyond a doubt, above half-a-century ago; and the following epitaph in the garden at Wilton House is a curious record of the particulars:--