8. STERNUM OR BREAST BONE.--This bone is small and short in the horse and is situated on the lower surface of the chest cavity. The principle points to be noted in this bone are that of its softness, and that the first eight pairs of ribs are attached to it on either side. This bone, in the horse resembles the keel and cut-water of a boat. 9. RIBS.--In the horse the ribs usually number eighteen on each side. They extend in a series of arches of varying curvature from the dorsal vertebrae above, towards the sternum and sides of the abdomen below. Their shape, in a great measure, determines the conformation or shape of the thorax or chest cavity; they protect its contents, and materially aid in its contraction and expansion. They are continued downward and forward by a small piece of cartilage or gristle, and are just slightly attached to the breast bone or sternum; these are called the false ribs. Note that, starting with the first rib, they get longer until the ninth rib is reached; they then get shorter, the last rib being only a few inches long. 10. SCAPULA OR SHOULDER BLADE.--The scapula is a flat bone situated on the antero-lateral (front side) surface of the thorax or chest cavity, it is triangular in shape, the base being turned upwards. The inferior or lower extremity articulates with the humerus or shoulder bone. 11. HUMERUS OR SHOULDER BONE.--The humerus is a long bone extending from the scapula to the radius and ulna in an oblique direction downwards and backwards. Like all long bones it possesses a shaft and two extremities and two articular surfaces. 12. RADIUS, OR BONE OF THE FORE-ARM.--The radius is a long bone, and occupies a vertical position between the humerus and the carpus. 13. ULNA, OR BONE OF THE FORE-ARM.--The ulna is an irregular bone, in form triangular, with the base uppermost, and is placed on the supero-posterior or (upper and back) part of the radius. 14. CARPUS, OR KNEE.--The carpus, knee or wrist, as it is incorrectly termed in quadrupeds, is composed of seven and often of eight small, irregular bones arranged in two rows of three each, one above the other, the seventh being at the back of the three in the upper row, and the eight, when present, in a similar position with respect to the lower row. Their names are as follows: scaphoid, lunar bone, cuneiform bone, trapezium, trapezoid, os magnus, unciform, pisiform, which is not always present. 15. OS METACARPI MAGNUS, METACARPAL OR CANNON BONE.--The large metacarpal, or cannon bone, is a long, straight bone, placed in a vertical direction. Its superior or upper extremity articulates with the carpus and its inferior or lower extremity articulates with the os suffraginis and the two sesamoids.