294 THE SKELETON OF THE RABBIT. 



of ribs have both capitular and tubercular articu- 

 lations with the vertebrae ; 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 con- 

 nected 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 

 ending 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 sternebrre. 



C. The Skiill. 



As in the dog-fish, the skeleton of the head is made up of 

 cranium proper, olfactory and auditory capsules, and visceral 

 skeleton, but the visceral skeleton, including jaws, hyoid bone, 

 and auditory ossicles, is in the rabbit so closely associated 

 with the other parts that it is convenient to describe the whole 

 of these partsmnder the general term ' skull.' 



In the adult rabbit, the original cartilaginous skull is al- 

 most completely replaced by bones. In addition to these carti- 



