[Illustration:
FIG. 23.—STERNUM AND COSTAL CARTILAGES OF HORSE, VENTRAL VIEW. (After
Ellenberger-Baum, Anat. f. Künstler.)
]
The first costal cartilage is an inch or more (2.5 to 3 cm.) in length.
The upper part is very wide and thick. The sternal end is small. The two
articulate with each other as well as with the sternum. The cartilages
of the other sternal ribs increase progressively in length and become
more rounded. The sternal end is expanded and has an elliptical convex
facet for articulation with the sternum. The cartilages of the asternal
ribs are long, slender, and pointed. The ninth is the longest, and is
very firmly attached to the eighth; behind this they diminish
progressively in size, and are attached to each other by elastic tissue.
Except in the case of the first, the cartilage does not continue the
direction of the rib, but forms with the latter an angle which is open
in front, and decreases in obtuseness from second to last.
More or less extensive ossification is to be regarded as a normal
occurrence, especially in the cartilages of the sternal ribs.