But in the molars, or at least in all but the lower carnassial, we find something quite different, namely, an interesting approximation to the semi-herbivorous type of dentition of the Bears. Both molars in the upper jaw, and the two last in the lower, have become _bonâ fide_ “grinders.” The scissor-like cutting edge has disappeared, and in place of it we have a hard crushing surface, raised into four cusps--two large external and two smaller internal ones. This has relation, of course, to the mixed character of the Dog’s food. The sectorial molar of the lower jaw still, however, retains its distinctive characters; its crown has much the same shape as in the Cat, but in addition possesses an extra lobe, in the shape of a large heel-like process projecting from its hinder border, and formed by a modification of its posterior cusp. [Illustration: SKELETON OF WOLF.] The Dog family have, as a rule, longish legs. They walk on the tip of their toes, like the Cats; but unlike the latter, their claws are not retractile. Curious to relate, however, the elastic ligament by which the drawing back of the feline claw is effected is present, but in so feeble a condition as to be quite incapable of antagonising the great flexor muscles. In consequence of this, the paw of a Dog is by no means such a perfect weapon as that of a Cat; and, as a matter of fact, the Dogs are distinguished from the Cats by their habit of always attacking the prey at once with their teeth, and never beginning the attack with a blow of the paw. In the matter of internal anatomy, the Dog family differ from all other Carnivores in possessing a large “blind gut,” or cæcum. The intestines, which are proportionally longer than a Cat’s, are, as usual, divided into large and small, and, at the place where the large and small intestines join one another, there goes off a folded sac, communicating with the intestine at one end, but quite closed at the other, forming, in fact, a small _cul-de-sac_. The use of this curious appendage is not properly understood, nor why it should be so well developed in the Dog family, while it is very small indeed in Cats, and wholly absent in Bears. No member of this family attains the size reached by some of the _Felidæ_, such as the Lion and Tiger, or some of the _Ursidæ_, such as the Grizzly or Polar Bear; the Mastiff is the largest of the tribe, no wild species of which is larger than an ordinary Shepherd’s Dog. THE DOMESTIC DOG.[92]