RIBS. -j 



CHARACTEES COMMON TO MOST 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 or capitulum ; it presents a superior and an inferior 

 oblique articular surface for articulation with the bodies of two vertebra, 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 neck, is the 

 tubercle, which is directed backwards, and presents a smooth surface for arti- 

 culation with the transverse process of the inferior of the two vertebrae with 

 which the head is connected, and, outside that, a roughness marking the 

 insertion of the posterior costo- trans verse ligament. The part termed the 

 necfc, between the head and the tubercle, is slenderer than the rest of the 

 rib. The whole extent beyond the tubercle constitutes the body. It becomes 

 laterally compressed, and wider from above downwards, towards the anterior 

 extremity. Outside the tubercle, between it and the most convex part of 

 the body, is a rough line, which corresponds to the outer border of the 

 erector spinee muscle, and which is termed the angle, because at this point 

 the curve of the rib is more sudden, and changes from an outward and 

 backward to a forward direction. The inferior border presents on its 

 inner aspect a groove, in which lie the intercostal vessels and nerve, and 

 which is best marked opposite the angle, and disappears in front. The 

 anterior extremity is hollowed at its tip into an oval pit, into which the 

 costal cartilage is implanted. 



Fig. 22. 



Fig, 22. THE FIRST, SIXTH, AND TWELFTH RIBS OP THE RIGHT SIDE. | 



A, the sixth seen from above and the outer side ; B, the same rib viewed from below 

 and within ; C, the first rib viewed from above and without ; D, the twelfth rib viewed 

 from above and within. 



1, the head in C & D, the ridge between the two facets of the head * *, in B ; 2, the 

 neck ; 3, the tubercle, in B presenting the rough tubercle and the smooth facet for 

 articulation with the transverse process ; 4, the lower border with the ridge and subcostal 

 groove ; 5, the upper border ; 6, the oval pit for the attachment of the costal cartilage ; 

 7, in the first rib, C, the scalene tubercle or spine, and near it the smooth groove for the 

 subclavian artery. 



Inclination and Curves. There is a general inclination of the ribs 

 downwards from the head to the anterior extremity. This slope is greatest 

 between the head and angle ; beyond that point it is diminished, and it is 

 again increased further forwards, and diminished at the anterior extremity. 

 The curve of the ribs is much more marked towards the back part than in 



