. The anatomy of the domestic animals. Veterinary anatomy. THE THORAX—THE OCCIPITAL BONE 49 ventral border is rounded, and is continuetl backward on the body of the bone. The dorsal border is concave ami has an articular cavity for the first pair of costal cartilages. The posterior extremity is formed by the xiphoid cartilage (Processus xiphoideus). This is a tliin plate, connected in front with the last hony segment by a relatively thick, narrow neck, and expanding in nearly circular form behind and laterally. Its dorsal surface is concave, and gives attachment to the diaphragm. The ventral s
. The anatomy of the domestic animals. Veterinary anatomy. THE THORAX—THE OCCIPITAL BONE 49 ventral border is rounded, and is continuetl backward on the body of the bone. The dorsal border is concave ami has an articular cavity for the first pair of costal cartilages. The posterior extremity is formed by the xiphoid cartilage (Processus xiphoideus). This is a tliin plate, connected in front with the last hony segment by a relatively thick, narrow neck, and expanding in nearly circular form behind and laterally. Its dorsal surface is concave, and gives attachment to the diaphragm. The ventral surface is convex and furnishes attachment to the transversus abdominis and the linea allm. The free margin is very thin. Development.—At birth the sternum of the horse consists of seven bony seg- ments termed sternebris, which are united by in- tersternebral cartilages. The last two sternebrae fuse in the second month, but the others do not usually unite completely even in old age. The sternebrte consist of very vascular spongy bone covered by a very thin layer of compact sub- stance. The adult sternum thus consists to a />-^'^WL Jj Ifcr" ^'''^^ very considerable extent of persisting cartilage, ri^^jp '^^Mk^T^X '''"'"'!"'" viz., the intersternebral cartilages, the ventral *"^ keel, and the extremities; in old age these under- go partial ossification. First rib THE THORAX The bony thorax of the horse is rcmarkal.)ly compressed laterally in its anterior part, but widens greatly behind. The anterior aperture (Apertura thoracis cranialis) is oval and very narrow below; in a horse of medium size its greatest width is about 4 inches (10 cm.), and its height 7 to 8 inches (ca. 18-20 cm.). The ventral wall (3r floor is about 16 inches (40 cm.) long, and the dorsal wall or roof about 38 to 40 inches (95-100 cm.) long. The height from the last seg- ment of the sternum to the seventh or eighth thoracic vertebra is about twice that of the anterior aiDer
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