56 ELEMENTARY BIOLOGY. [CHAP. 



a. Examine carefully and draw various aspects of a 

 detached vertebra^ say the third. 



a. Its soHd flattened ventral part {centru?n)^ with 

 an anterior concave and a pdsterior convex 

 surface {proccelous). 

 /?. The neural arch : an arch of bone arising from 

 the centrum dorso-laterally. It furnishes the 

 undermentioned. 



The transverse process : a bony bar arising on 

 each side from the base of the arch and passing 

 outwards and a little downwards. 



The arlicidar processes {zygapophyses) ; an an- 

 terior and posterior pair, springing from the 

 sides of the arch ; the anterior {pre-zygapophyses) 

 having their smooth articular surfaces directed 

 upwards ; the posterior {post-zygapophyses) with 

 similar surfaces directed downwards. 



The short spinous process ; springing from the 

 dorsal aspect of the arch and directed back- 

 wards. 



y. The neural canal ; bounded, above and at the 

 sides by the arch, below by the centrum. 



b. Examine the remaining vertebrae. 



a. The first vertebra : its body^ produced forwards 

 into a wedge-shaped process {odo?itoid process) 

 which lies between the occipital condyles of 

 the skull : its arch^ usually incompletely ossified 

 in the region of the spinous process, which is 

 rudimentary; posterior zygapophyses alone pre- 

 sent : the large concave anterior facets {condylar 

 facets), partly on the arch and partly on the 

 centrum, for articulation with the skull. 



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