266 SKELETON OF THE EABBIT 



of the corresponding vertebra; and imme- 

 diately beyond the tubercle is a short vertical 

 projection for the attachment of ligaments. 

 ii, The sternal portion is a short bar of calcined or 

 imperfectly ossified cartilage, connecting the 

 lower end of the vertebral portion with the 

 sternum. 



b. The ribs in general. The ribs increase in length 

 from the first, which is very short, to the sixth, 

 behind which they diminish. The first nine pairs 

 of ribs have both capitular and tubercular articu- 

 lations with the vertebra : in the remaining three 

 (or four) pairs, which are more slender than the 

 anterior ones, the tubercles are absent, and the 

 capitular articulations, which alone are present, 

 are confined to the corresponding vertebrae. 



The sternal portions of the first seven pairs 

 articulate directly with the sternum : the remain- 

 ing ones do not reach the sternum, though those 

 of the eighth and ninth pairs are closely connected 

 with the ribs in front of them. 



2. The sternum is an elongated, laterally compressed median 

 rod, situated in the ventral wall of the thorax, and 

 divided transversely into segments or sternebrae. It 

 is developed in connection with the ventral ends 

 of the ribs, and consists at first of right and left 

 halves. 



The anterior segment or manubrium is much the 

 largest, and is produced ventrally and in front into a 

 prominent keel. 



Behind the manubrium come four segments of 

 about equal length, then a very short segment, and 

 finally the xiphisternum, a long slender bony rod end- 

 ing behind in a horizontal plate of cartilage. 



The first pair of ribs articulate with the sides of 

 the manubrium, and the succeeding six pairs between 

 the several sternebras. 



