THE RIBS 73 



always prominent, and servos as a landmark for the second 

 rib. 



The body is longer, narrower, and thinner than the manu- 

 brium, and tapers toward its lower end. It is marked on its 

 anterior surface by three slight transverse ridges; otherwise 

 it is quite flat. This surface gives attachment to a part of the 

 aponeurosis of the pectoralis major of each side. The posterior 

 surface is slightly concave and marked by the same lines as 

 anteriorly, but less distinctly, and gives attachment below to 

 the triangularis sterni of each side. 



Each lateral margin presents four notches and two half- 

 notches; they approach each other from above down, being 

 separated by curved intervals. The half-notch above is for 

 the second cartilage; the notches for the third, fourth, and 

 fifth cartilages are opposite the line of junction of the four 

 segments; the notch for the sixth cartilage and the half-notch 

 for the seventh belong to the inferior segment. So most of 

 the cartilages of the true ribs articulate in front at junctions 

 of segments, analogous to the connection of ribs with the 

 vertebral column. 



The ensiform process (metasternum) projects down between 

 the cartilages of the seventh rib. It has various forms, is usually 

 more or less triangular, and may be bent forward, backward, 

 or laterally, be forked or perforated, and is cartilaginous dur- 

 ing youth. At its upper angle is a half -notch for the seventh 

 cartilage. 



Its anterior surface has attached the chondroxiphoid liga- 

 ments. Its posterior surface gives attachment to some fibers 

 of the diaphragm and triangularis sterni muscles. Its lateral 

 borders afford attachment to parts of the aponeurosis of the 

 abdominal muscles. To the apex is inserted the upper end 

 of the linea alba. 



THE RIBS 



The ribs (costse) are twelve in number on each side. They 

 are obliquely placed, running forward and downward. The 

 obliquity increases from above downward to the ninth rib, 

 where it reaches its maximum; from there downward it de- 

 creases. 



The first seven pairs, attached by costal cartilages to the 



