SPINAL COLUMN. 



133 



The upper convexity is formed by the lower cervical and the 

 upper dorsal vertebrae, and the lower convexity by the lum- 



Fig. 123. 



bar vertebrae ; whilst the central conca- 

 vity is formed by the middle dorsal ver- 

 tebrae. Behind the centra we see the 

 lateral holes for giving transit to the spinal 

 nerves, and formed by the junction of the 

 notches in the neurapophyses. The direc- 

 tion of the neurapophyses and parapophy- 

 ses is likewise well seen in this figure. 



[ 260. The following table* shows the 

 number of the vertebrae in the different 

 regions of the spinal column, in a few 

 familiar examples from mammals, birds, 

 reptiles, and fishes. It is important to 

 note, that the number seven prevails in 

 the cervical vertebrae of all mammals, 

 whether we study these bones in the rudi- 

 mentary condition in which they exist in 

 whales, or in the enormous development 

 they attain in the neck of the giraffe. 

 The increased number of the bones in 

 the same region, in birds, is a compensa- 

 tion for the want of anterior prehensile 

 members, the neck, in birds, being used 

 as an arm. The number of the dorsal 

 vertebrae ranges from 7 to 320 ; the lum- 

 bar, from 2 to 9 ; and the coccygeal, from 

 4 to 115. The table might have been 

 greatly extended ; but those who wish for 

 further information on this interesting 

 branch of comparative osteology, are re- 

 ferred to the great work from which it is 

 extracted : 



* Cuvier, Lecons D'Anatomie Comparee, torn. i. 



