In the skeleton of the dog and in that of the horse, as well as of all other animals remarkable for their speed, there is a peculiar characteristic of the chest which deserves to be noticed. A narrow-chested horse or dog may have better wind than another with a round barrel, because he is able to alter the cubic contents of his chest more rapidly, and thus inspire and expire a larger volume of air. A medium transverse diameter is therefore to be desired, and is practically found to be advantageous, in allowing a better action of the shoulder blades rolling upon the surface on each side. These facts ought to be taken into consideration in selecting the best kind of frame for the purposes of speed and endurance.

Large size of bone contributes to the strength of the limbs, and foxhounds especially, which have continual blows and strains in their scrambling over or through fences of all kinds, require big limbs and joints. When, however, extreme speed is desired, as in the greyhound, there may be an excess of bone, which then acts as an incumbrance, and impedes the activity. Still, even in this dog, the bones and joints must be strong enough to resist the shocks of the course, without which we constantly find them liable to fracture or dislocation. If, however, a dog is brought up at liberty, and from his earliest years is encouraged in his play, the bones, though small, are strong, and the joints are united by firm ligaments which will seldom give way. 287

The dog has no collar-bone, so that his fore quarter is only attached to the body by muscular tissue. This is effected chiefly by a broad sling of muscle, which is attached above to the edge of the shoulder-blade, and below to the ribs near their lower ends. It is also moved backwards by muscles attached to the spine, and forwards by others connected in front to the neck and head, so that at the will of the animal it plays freely in all directions.

The teeth are 42 in number, arranged as follows: