The first seven pairs are connected with the sternum; the next three are each articulated with the lower border of the cartilage of the preceding rib; the last two have pointed extremities, which end in the wall of the abdomen.

They are broad at their attachments to the ribs, and taper toward their sternal extremities, excepting the first two, which are of the same breadth throughout, and the sixth, seventh, and eighth, which are enlarged where their margins are in contact.

The anterior surface is convex, and looks forward and upward: that of the first gives attachment to the costoclavicular ligament and the subclavius muscle; those of the first six or seven at their sternal ends, to the pectoralis major.

The inferior borders of the sixth, seventh, eighth, and ninth cartilages present heel-like projections at the points of greatest convexity.

The contiguous borders of the sixth, seventh, and eighth, and sometimes those of the ninth and tenth, costal cartilages articulate with each other by small, smooth, oblong facets.

[7] This article incorporates text in the public domain from page 127 of the 20th edition of Gray's Anatomy (1918)