. The anatomy of the human body. Human anatomy; Anatomy. COSTAL CARTILAGES. 69 base; and, lastly, to certain peculiarities of conformation in the first, second, third, elev- enth, and twelfth ribs, which require special description. The first rib {I, fig. 38, and fig. 40) is the shortest, and proportionally the broadest of all the ribs, thus forming an imperfect lid to the bony case which constitutes the thorax. Its edges are- curved, but its surfaces are flat. The curve which it describes forms part of the circum- ference of a much smaller circle than any of the other ribs. The posterior extr
. The anatomy of the human body. Human anatomy; Anatomy. COSTAL CARTILAGES. 69 base; and, lastly, to certain peculiarities of conformation in the first, second, third, elev- enth, and twelfth ribs, which require special description. The first rib {I, fig. 38, and fig. 40) is the shortest, and proportionally the broadest of all the ribs, thus forming an imperfect lid to the bony case which constitutes the thorax. Its edges are- curved, but its surfaces are flat. The curve which it describes forms part of the circum- ference of a much smaller circle than any of the other ribs. The posterior extremity has a small head with a single convex* facette {a, fig. 40), supported by a long, thin, and cylindrical neck (b). The tubercle {c) is very prominent; it occupies the external bor- der, and gives an angular appearance to this rib. The anterior extremity {d) is broader than that of any other rib. Of the two surfaces, one is directed upward and slightly outward, the other downward and a little inward. The superior surface {fig. 40) has two depressions separated by a tuberosity (e). The anterior corre- sponds to the subclavian vein ; the posterior to the artery of the same name. The tu- berosity which separates them gives attachment to the anterior scalenus muscle. The internal edge (a e d) is concave; the external {a c d) is convex, and has no groove. The first rib has neither a curvature of torsion, nor an angle ; so that the whole of it can rest upon the same horizontal plane. The superior surface presents, also, near its anterior extremity, a depression, which appears to result from pressure by the clavicle, which I have seen, in some cases, immediately articulated with this bone. The second rib (2, fig. 38) preserves many of the characters of the preceding, but dif- fers essentially in its length, which is at least double ; it belongs to a much larger circle : it has no curvature of torsion, and can rest upon the same plane with its two ends ; the angle is scarcely visib
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