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PECULIARITIES IN THE ANATOMY AND PHYSIOLOGY OF THE DOG.
The Skeleton including the Teeth.—The Muscular System. The Brain and Nervous System.— The Digestive System.— The Heart and Lungs.— The Skin,
THE SKELETON*, INCLUDING THE TEETH.
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 formation of the chest which deserves to be noticed. The principle of construction in every thorax, as this part is called scientifically, is that of dilatation and contraction, by which its entire contents are lessened or increased, and thereby air is made to pass in and out. In man this is chiefly caused by the front of the chest rising and falling, and in this way increasing the diameter from before backwards, but in the dog, horse, deer, &c., the increase is from side to side, the ribs being sickle-shaped, and acting laterally like the gill-covers of a fish. From this it often arises that 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 round barrel is nearly at its greatest expansion, and though it can contract it cannot dilate its volume, while the chest that is too flat can expand rapidly, but then it
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a, a, a. The ligamentum nuchæ.
22, 22. Twenty caudal vertebræ – verte1. II. III. IV. V. VI. VII. The seven ver
bræ of the tail. tebræ of the neck.
23. The left os innominatum. 13. The thirteen dorsal vertebræ.
24. Right ditto. 7. The seven lumbar vertebræ.
The nine true ribs, with their cartilages. 21. Os sacrum, or rump-bone.
The four false ribs, with their cartilages. 0,0. The sternum.
THE LEFT ANTERIOR EXTREMITY.
1. The scapula, or shoulder-blade.
11. Os metacarpi digiti quarti -- fourth
THE RIGHT ANTERIOR EXTREMITY. 1. Radius.
9. Ossa metacarpi digitorum quatuor 2. Ulna.
- the four bones of the meta3. Os triquetrum—the triangular bone.
carpus. 6. Os semilunare—the semilunar bone. 10. Phalanx prima pollicis—first phalange 6. Os multangulum majus — the larger of the thumb. multangular bone.
11. Phalanx tertia pollicis-third phalange 7. Os multangulum minus — the small of ditto. multangular bone.
12. Digiti quatuor-phalanges of the four 8. Os metacarpi pollicis—the thumb.
has not the power of contraction beyond its natural limits. 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. On the other hand, man requires great depth of chest from before backwards if he is to have good wind, and the lateral diameter is of less importance. 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 so much lumber, 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.
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