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

The rough tubercle of the ribs

On this outer surface of the ribs where they first leave the transverse processes of the vertebrae, there is seen a rough, uneven tubercle [t. costae] (O in figs. 4 and 5) made to receive the tendons of the eleventh muscle [m. erector spinae, m. longissimus thoracis] that moves the back (D in the 12th table of muscles). The tendons of this muscle are inserted partly into the tips of the transverse processes, and partly into these costal tubercles. Then, where the ribs depart still further from the transverse processes of the vertebrae, they are rough and uneven in this outer, posterior surface [angulus costae] (R in figure 4) and even have a certain rather prominent swelling of sorts to make a suitable point of insertion for the muscle which we shall count the fourth [m. erector spinae, m. iliocostalis thoracis] of the muscles that move the thorax in man, and the sixth in apes and dogs. 49 Not only is this roughness suitable for the insertion of that muscle, but it will be explained that the outer intercostal muscles [m. intercostalis externus] (V in the 11th table of muscles) originate here: these muscles originate in this region next to the vertebrae and run not only from the lower part of the upper rib toward the upper part of the rib below, but also from the outer part of one rib to the outer part of the other. Elsewhere the ribs are smooth and even, unless one were to argue that they are slightly rough on their upper and lower surface where the origin and insertion of the intercostal muscles takes place. On its upper surface where it is very wide, the first rib is characteristically rough and uneven so that the fourth of the muscles that move the back (C in the 8th table of muscles [m. scalenus anterior]) may conveniently take its beginning here.



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