THE PECULIAR RIBS 75 



faces, external and internal, and two borders, superior and 

 inferior. On the external surface, close in front of the tuberosity, 

 over the most convex portion of the rib, is found an oblique 

 rough line, directed downward and outward, corresponding 

 to the outer border of the iliocostalis muscle, marking the 

 angle. The interval separating the tuberosity and the angle 

 increases from the second to the tenth rib. The anterior angle 

 is found near the sternal end of this surface. 



The internal surface is smooth, concave, directed slightly 

 upward behind the angle, and slightly downward in front of it. 



The superior border is thick and rounded, and presents an 

 external and an internal lip, for the attachment of the external 

 and internal intercostal muscles. 



The inferior border presents the subcostal groove, best 

 marked at the angle disappearing in front. Its external lip 

 is much the more prominent, and gives attachment to the 

 external intercostal muscle. The inner or superior lip of this 

 groove is rounded and gives attachment to the internal inter- 

 costal. The groove itself lodges the intercostal vessels and 

 nerve. 



Starting from the upper and inner border of the neck is 

 a superior costal groove, soon lost on the body. 



The anterior extremity is hollowed into a pit for union with 

 the costal cartilage. The ribs are curved on three axes a 

 vertical one near the angle; also a transverse one at this place, 

 so that when the anterior part of the rib is horizontal the 

 posterior will rise up ; and a longitudinal one, so that the anterior 

 part looks up and the posterior part looks down. 



The seventh or eighth rib is the longest, after which the 

 ribs decrease to the twelfth. The first is broadest, and the 

 twelfth narrowest. 



The Peculiar Ribs 



The peculiar ribs are first, second, tenth, eleventh, and 

 twelfth. 



The first rib is short and not twisted, yet one of the most 

 curved. Its surfaces look nearly up and down. The head is 

 small and has a single articular facet. The neck is slender 

 and rounded, and the angle coincides with the tuberosity, 

 which is strong and placed on the outer margin of the rib. 

 At this point there is a slight bend in the rib, with the con- 



