6 THE THORAX. 



General characters of the ribs. These are best marked in the ribs near the 

 middle of the series. The posterior extremity is thickened, and is termed the head 



TUBEROSITY 

 NON-ARTICULAR PART 



or capitulum ; it presents a superior and an inferior 

 oblique articular surface for articulation with the 

 bodies of two vertebrae, and, between them, a slight 

 ridge, to which the interarticular ligament is attached. 

 At a little distance from the head, and separated from 

 it by the slightly constricted neck, is the tuberosity, 

 an oval eminence Avhich is divided into two parts by 

 an oblique groove ; the inner part is smooth and 

 articulates with the transverse process of the lower of 



Fig. 26. FIFTH RIB OF THE RIGHT SIDE, FROM BEHIND. 

 (Drawn by D. Gunn.) | 



the two vertebrae with which the head is connected, 



while the outer part is rough and serves for the 



attachment of the posterior costo-transverse ligament. 



The whole extent beyond the tuberosity constitutes 



the body. It is laterally compressed, and broader 



from above downwards towards the anterior extremity. 



Outside the tuberosity, over the most convex part of 



the body, is a rough line which corresponds to the 



outer border of the erector spinae muscle, and marks 



the angle, so called because at this point the rib takes 



a more sudden curve, its direction being now forwards 



and outwards. The inferior border presents on its 



inner aspect the subcostal groove, in which lie the 



intercostal vessels and nerve, and which is best 



marked opposite the angle and disappears in front. 



The anterior extremity of each rib is hollowed at its tip into an oval pit, in which 



the costal cartilage is implanted. 



Inclination and curves. There is a general inclination of the ribs downwards 

 from the head to the anterior extremity, the slope being greatest between the head 



Fig. 25. FIFTH RIB OF THE RIGHT 

 SIDE, FROM BELOW. (Drawn by 

 D. Gunn.) 



