Skull. 89 



There are three salient points of structure which distinguish 

 the vertebral column of the rabbit from that of the bird. In 

 the first place, the centrum is ossified in three pieces — a central 

 one and two epiphyses (one at each end)j secondly, the 

 surfaces of articulation are flat instead of saddle-shaped; 

 thirdly, the first vertebra (the atlas) articulates with the skull 

 by two facets, instead of only one, as in the bird. The axis, 

 or epistropheus, is like that of the bird in having a peg-like 

 odontoid process — really the centrum of the atlas. The dorsal 

 vertebrse have very long spinous processes, associated with 

 strong muscles to hold and move the heavy head. The 

 lumbar vertebrae have very long lateral processes known as 

 metapophyses. The rabbit has twelve, sometimes thirteen, 

 pairs of ribs; of these the eight anterior are borne by two 

 heads, the capitulum and the tuberculum. The former is 

 articulated with a small semi-lunar facet on the junction of 

 each successive pair of centra; the seventh cervical vertebra 

 bears the half of the first of these facets. The last four 

 vertebras lack the tubercular head upon the transverse pro- 

 cesses ; they have only the capitular head. Seven ribs reach 

 the sternum. 



Skull. 



The skull was at one time regarded as a single structure, 

 formed of a number of coalesced and modified vertebrae. The 

 anatomical knowledge and genius of Goethe and Owen 

 succeeded in impressing this view of its nature upon com- 

 parative anatomists, until the theory was finally overthrown by 

 Huxley in 1858. The skull is now known to be composed of 

 a series of elements which have primarily no connection with 

 each other. It is built up of — 



1. The originally cartilaginous and afterwards, in all 

 animals above the elasmobranch fishes, ossified brain-case or 

 cranium proper. 



2. Of the cartilaginous (or ossified) capsules of the three 

 organs of special sense — the auditory, olfactory, and optic. 



3. Of portions of, at least, the first two of the visceral 



