The spine of the dog consists of seven vertebrae in the neck, thirteen in the back, seven in the loins, three sacral vertebrae, and twenty to twenty-two in the tail. In both the dog and the wolf there are thirteen pairs of ribs, nine true and four false. Each has forty-two teeth. They both have five front and four hind toes, while outwardly the common wolf has so much the appearance of a large, bare-boned dog, that a popular description of the one would serve for the other.
Nor are their habits different. The wolf's natural voice is a loud howl, but when confined with dogs he will learn to bark. Although he is carnivorous, he will also eat vegetables, and when sickly he will nibble grass. In the chase, a pack of wolves will divide into parties, one following the trail of the quarry, the other endeavouring to intercept its retreat, exercising a considerable amount of strategy, a trait which is exhibited by many of our sporting dogs and terriers when hunting in teams.
A further important point of resemblance between the Canis lupus and the Canis familiaris lies in the fact that the period of gestation in both species is sixty-three days. There are from three to nine cubs in a wolf's litter, and these are blind for twenty-one days. They are suckled for two months, but at the end of that time they are able to eat half-digested flesh disgorged for them by their dam or even their sire.
The native dogs of all regions approximate closely in size, coloration, form, and habit to the native wolf of those regions. Of this most important circumstance there are far too many instances to allow of its being looked upon as a mere coincidence. Sir John Richardson, writing in 1829, observed that "the resemblance between the North American wolves and the domestic dog of the Indians is so great that the size and strength of the wolf seems to be the only difference.
It has been suggested that the one incontrovertible argument against the lupine relationship of the dog is the fact that all domestic dogs bark, while all wild Canidae express their feelings only by howls. But the difficulty here is not so great as it seems, since we know that jackals, wild dogs, and wolf pups reared by bitches readily acquire the habit. On the other hand, domestic dogs allowed to run wild forget how to bark, while there are some which have not yet learned so to express themselves.
The presence or absence of the habit of barking cannot, then, be regarded as an argument in deciding the question concerning the origin of the dog. This stumbling block consequently disappears, leaving us in the position of agreeing with Darwin, whose final hypothesis was that "it is highly probable that the domestic dogs of the world have descended from two good species of wolf (C. lupus and C. latrans), and from two or three other doubtful species of wolves namely, the European, Indian, and North African forms; from at least one or two South American canine species; from several races or species of jackal; and perhaps from one or more extinct species"; and that the blood of these, in some cases mingled together, flows in the veins of our domestic breeds.
