Some knowledge of the skeleton is advisable to facilitate the study of diseases of bones and the accidental injuries to which they are exposed. The skeleton of the adult ox is made up of the following number of bones:
| Spinal column | 45 | |
| Head | 28 | |
| Chest | 27 | |
| Shoulder | 2— | 1 on each side. |
| Arm | 2— | 1 on each side. |
| Forearm | 4— | 2 on each side. |
| Forefoot | 40— | 20 on each side. |
| Pelvis | 2— | 1 on each side. |
| Thigh | 2— | 1 on each side. |
| Leg | 6— | 3 on each side. |
| Hind foot | 38— | 19 on each side. |
| ——— | ||
| Total | 196 |
Without attempting to burden the reader with the technical names and a scientific classification of each, it appears desirable to describe some of the characteristics of forms in general and of a few classes into which they may be divided, leaving the special study of individual bones to the illustrations of the skeleton ([Pl. XXV]), which will serve better than a great deal of writing to fix in the mind of the reader the location, relation, and function of each one. In early fetal life the place of bone is supplied by temporary cartilage, which gradually changes to bone. For convenience of study, bones may be said to be composed of a form of dense connective tissue impregnated with lime salts and to contain two elementary constituents—the organic or animal and the inorganic or earthy. In young animals the former predominates; with increasing years the relative proportions of the two change, so that when advanced age is reached the proportion of inorganic far exceeds the organic. The gradual change with advancing years from organic to inorganic has the effect of rendering the bone harder and more brittle, and though it is stronger, the reparative process is slower when injury does occur.
The bones are nourished in two ways: First, from the outside through their covering, called the periosteum—the thin, strong membrane that covers every part of the bone except the articular surface of the joints; and, second, from within through the minute branches of blood vessels which pass into the bones through holes (foramina) on their surface and are distributed in the soft structure (medulla) of the inside. The structure of the bone is divided into two parts—the compact or hard material of the outside, which gives strength and is more abundant in the shafts of long bones, and the cancellated, softer tissue of the inside, which affords accommodation to the blood vessels necessary for the nourishment of that part of the structure.
In shape, bones are divided into three classes—long, flat, and short. The long bones are the ribs and those mostly found in the limbs; the flat bones are found in the head, the shoulder, and the pelvis; the short bones in the spinal column and in the lower portions of the limbs.
With this little introduction, which seems almost indispensable, we will proceed at once to the consideration of diseases of bones, for they undergo disease processes like any other living tissue.
OSTEITIS.
Inflammation of the compact structure of bones (osteitis) may be either acute or chronic, and may involve the whole extent of the bone affected or may be confined to only a portion of it. This inflammation results from injury, such as concussion, laceration, or a crushing bruise; also from specific influences, as in actinomycosis (lumpy jaw) or cases of foul foot. The latter affection frequently involves the bones, and for this reason the pastern is the most frequent seat of osteitis. There is dull pain on pressure and a painful swelling of bone when pus is present. Suppuration may involve the overlying soft tissues, causing an abscess, which may finally break through the skin. The inflammatory condition sometimes assumes an ulcerated form (caries) or from interrupted nutrition of the part deprived of the blood necessary to its nourishment may cause death of a large section of bone (necrosis); this dead fragment (sequestrum), becoming separated from the main portion of bone, acts as a foreign body.
Treatment—This consists in resting the affected part and in giving vent at the earliest possible moment to whatever pus may be present. Free drainage should then be maintained. Apply dressings of lactic acid or inject with 5 per cent zinc-chlorid solution and pack with tampons of cotton soaked in antiseptic solutions. A laxative to keep the bowels moving freely is the only internal treatment necessary.