Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 19 On the Bones of the Thorax

Smoothness and roughness of the ribs; their sulcus

The ribs do not have the same smoothness throughout. On their inner surface, where they face the membrane [pleura parietalis, pars costalis] that surrounds them, they all appear smooth and not in the least rough; but the third and those that follow as far as the tenth present a depression [sulcus costae] on their inner surface towards the bottom (K in figs. 1 and 4), carved along their length, not actually visible throughout the length of the rib but most evident where they first leave the vertebrae and begin to run toward the sides of the thorax. This depression is prepared for a branch (G, G in the fig. for ch. 6, Bk. 3) [vena intercostalis posterior] of the hollow vein [v. azygos] which the unpaired vein extends to the ribs; it also carries a branch (k, k in the fig. for ch. 11, Bk. 3) [a. intercostalis posterior] of the great artery [pars descendens aortae], and the nerve (the principal branches [nervi thoracici, rami anteriores, nervi intercostales] following the course of the ribs in fig. 2, ch. 11, Bk. 4) [n. intercostalis] originating from the dorsal medulla. [medulla spinalis]. But because these vessels are large in the middle ribs and always run as a matched set while in the three upper ribs they are small and run a wandering course, it comes as no surprise that the middle ribs have these depressions but the upper ribs do not. The three lower ribs, though large vessels are extended to them, are thin and concave on their inner surface and they still provide safe passage to those vessels without the aid of those depressions. This depression, carved for the passage of vessels, makes the lower part of the rib sharper and thinner than the upper, which looks more blunt and (so to speak) more smoothly rounded. The outer surface of the ribs, which is convex,


page 91

is not smooth everywhere. Where the ribs are attached to the vertebrae (L, M, and especially Q in fig. 4), excluding what is made up by the tubercles and capitula by which the ribs are articulated to the depressions 48 in the vertebrae, they are rough and uneven, so that ligaments which attach the ribs to the vertebral bodies and their transverse processes may better be attached.



Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 19 On the Bones of the Thorax