THE THORAX. 109 



curvature somewhat abrupt, takes place, which is the angle of 

 the rib. Between the angle and the transverse process of the 

 vertebra, each rib is rather more narrow and cylindrical than it 

 is in advance of the angle. The superior margin of the rib is 

 rounded and somewhat rough, for the insertion of the intercostal 

 muscles, while the inferior margin is brought to a thin, cutting 

 edge. Just within, and above 'the latter, is a fossa beginning 

 somewhat nearer to the spine than the angle of the rib, and 

 ceasing about one-third of the whole length of the rib, short of 

 its anterior extremity. It contains the intercostal vessels and 

 nerve. From the upper margin of this fossa arises the internal 

 intercostal muscle, and from the lower the external. 



The anterior extremities of the ribs are thin and flattened, 

 in the upper eight there is some increase in their breadth at 

 this point, and in all there is an oblong pit for receiving the end 

 of the corresponding cartilage. The vertebral extremity of the 

 rib is its head, and presents two flat articular surfaces, separated 

 by a ridge. This head is received into the inter-vertebral mat- 

 ter, and upon the articular faces of the adjoining margins of the 

 vertebrae. A small depression exists upon the posterior face of 

 the rib bordering on its head, for containing a little fatty mass. 

 About an inch beyond the head, at the posterior under surface 

 of the rib, is a tubercle, presenting a smooth articular face, for 

 connecting itself with the transverse process of the vertebra. 

 Just beyond this, but bordering on it, is a much smaller tuber- 

 cle, not unfrequently indistinct, for the insertion of the exter- 

 nal transverse ligament, and below it is a small pit for the lodge- 

 ment of fatty matter near the joint. The space between the 

 greater tubercle and the head of the rib is its neck, which is in 

 contact with the antero-superior face of the transverse process 

 of the vertebra, and has a sharp ridge on its upper margin, for the 

 insertion of the internal transverse ligament. 



The most of the ribs have a very sensible twist in them, by 

 which their spinal extremity is directed upwards, and the ster- 

 nal extremity downwards; from which it results, that the whole 

 length of the rib cannot be brought into contact with a hori- 

 zontal plane. 



Differences in Ribs. Though there are many common points 

 VOL. I. 10 



