124 



)LOGY 





the tubercle ; it consists of an articular and a non-articular portion. The articular 

 portion, the lower and more medial of the two, presents a small, oval surface ibr 



Angle 



Non-articular part of tubercle 



Articular part of tubercle 



FIG. 122. A central rib of the left side. 

 Inferior aspect. 



articulation with the end of the transverse pro- 

 cess of the lower of the two vertebra? to which 

 the head is connected. The non-articular por- 

 tion is a rough elevation, and affords attach- 

 ment to the ligament of the tubercle. The 

 tubercle is much more prominent in the upper 

 than in the lower ribs. 



Body. The body or shaft is thin and flat, 

 with two surfaces, an external and an internal ; 

 and two borders, a superior and an inferior. 

 The external surface is convex, smooth, and 

 marked, a little in front of the tubercle, by a 

 prominent line, directed downward and lateral- 

 ward; this gives attachment to a tendon of 

 the Iliocostalis, and is called the angle. At 

 this point the rib is bent in two directions, 

 and at the same time twisted on its long axis. 

 If the rib be laid upon its lower border, the 

 portion of the body in front of the angle rests 

 upon this border, while the portion behind the 

 angle is bent medialward and at the same 

 time tilted upward; as the result of the twist- 

 ing, the external surface, behind the angle, 

 looks downward, and in front of the angle, 

 slightly upward. The distance between the 

 angle and the tubercle is progressively greater 

 from the second to the tenth ribs. The por- 

 tion between the angle and the tubercle is 

 rounded, rough, and irregular, and serves for 

 the attachment of the Longissimus dorsi. The 

 internal surface is concave, smooth, directed a 

 little upward behind the angle, a little down- 

 ward in front of it, and is marked by a ridge 

 which commences at the lower extremity of 

 the head; this ridge is strongly marked as far 

 as the angle, and gradually becomes lost at 

 the junction of the anterior and middle thirds 

 of the bone. Between it and the inferior 

 border is a groove, the costal groove, for the 

 intercostal vessels and nerve. At the back 

 part of the bone, this groove belongs to the 



