SKELETON OF RABBIT 



789 



The first seven pairs articulate with the breast-bone, the 

 eighth and ninth are connected to the ribs in front, the 

 others are free. Any one of the first seven or more typical 

 ribs consists of two parts, a vertebral portion articulating 

 with a vertebra, an imperfectly ossified sternal portion 

 connecting the end of the vertebral portion with the 

 sternum. Each of the first nine ribs has a double head — 

 the capitulum articulating with the centrum of the corre- 

 sponding vertebra, and partly with that of the one in front, 

 the tubercle articulating with the transverse process of the 



inx. 



Fig. 472. — Side view of rabbit's skull. 



Pmx., Premaxilla ; Na., nasal ; Fr., frontal ; Pa., parietal ; Sq., 

 squamosal ; S.O., supraoccipital ; Per., periotic ; 7'., tympanic 

 (the reference line points to the bony external auditory meatus, 

 beneath it Lies the inflated bulla) ; P.O., paroccipital process. 



corresponding vertebra. The posterior ribs have no 

 tubercles, and the capitular articulations are restricted 

 to the corresponding vertebrae. 



The sternum is a narrow jointed plate, with a large keeled 

 presternum or manubrium, then five segments composing 

 the mesosternum, then a posterior xiphisternum ending in 

 cartilage. 



The skull consists, as in all the higher Vertebrates, of two 

 sets of bones — cartilage bones preformed in the cartilage of 

 the original gristly brain-box and its associated arches, and 

 membrane bones developing in the investing membrane and 



