VERTEBRAE OF RABBIT. 15 



elastic ligamentum nuchae which supports, the head. It has no anterior 

 articulating processes upon its neural arch in mammals, but it comes into ar- 

 ticular relation with the atlas by means of two oblique zygapophysial surfaces 

 developed on either side of the base and a third on the front of its odontoid 

 process, which is the backwardly displaced and anchylosed centrum of that 

 vertebra. It is the deepest from above downwards, and the longest from 

 before backwards, but also the narrowest from side to side of the cervical 

 series. The first two cervical vertebrae articulate with each other and with 

 the occiput by means of synovial joints as the neurapophysial processes are 

 articulated to each other throughout the rest of the trunk, where however 

 the centra are connected by interarticular fibrocartilaginous discs containing 

 in their central pulp remnants of the primitive chorda dorsalis. The neural 

 spines of the third and fourth cervical vertebrae are low but long, corre- 

 sponding with the long neural roof which these two vertebrae possess ; the 

 spines of the shorter neural arches of the fifth, sixth, and seventh vertebrae 

 have more of the shape which their name implies. The lateral processes or 

 ' cervical ribs ' of these vertebrae are greatly developed ; those of the atlas 

 more or less obliquely outwards, those of the axis backwards ; those of the 

 third, fourth, fifth, and sixth, both anteriorly and posteriorly, and those of 

 the seventh outwardly. The fourth, fifth, sixth, and seventh have prominent 

 upgrowths developed on this process or rib which are homologous apparently 

 with the prominent tubercles of the ribs of these creatures, or, possibly, 

 with the metapophyses of the trunk vertebrae. This process makes up by 

 itself almost the whole of the transverse process of the seventh cervical 

 vertebra, the inferior, antero-posteriorly-produced, process, which is much 

 larger in the preceding vertebrae and largest of all in the one immediately 

 preceding, being lost in this, the last of the series. These inferior elements 

 of the transverse processes, by bending inwards form with the vertebral 

 bodies furrows, in which the long anterior neck muscles are lodged, a central 

 slightly-raised line marking the line of separation of these muscles and 

 representing the homologously-placed hypapophyses of certain lower verte- 

 brata. The segment of bone which completes the ring of the atlas anteriorly 

 is homologous with these hypapophysial downgrowths. The last cervical 

 vertebra in the Rabbit has not, as it has in the Rat, any connection with 

 the tubercle of the first dorsal rib. 



Eight of the dorsal vertebrae, from the second to the ninth inclusively, 

 have, each, two half facets on their centra, the first has one whole facet 

 anteriorly and a half facet posteriorly, and the tenth, eleventh, and twelfth 

 have, each of them, single whole facets placed on the anterior superior angle of 

 the lateral aspect of their centra, for articulation with the heads of the ribs. 

 The neural spines of the dorsal vertebrae are largely developed, their apices 

 from the second to the ninth showing a tendency to become bifid antero- 

 posteriorly. The tenth is the anticlinal vertebra (for which, see p. 8, supra}, 



