508 



HISTORY OF THE HUMAN BODY 



one ; the Golden Age idea appearing in Anatomy, but here, as 

 everywhere else, the reverse of actual history. Yet this dia- 

 gram, although erroneous as an explanation of early con- 

 ditions, represents in a clear manner the parts that appear in 

 actual cases, especially in the higher forms, and as such has 

 been taken as the foundation of our modern nomenclature. 

 This typical vertebra consists of a cylindrical centrum, fur- 

 nished with a neural arch, a hcemal arch and several lateral ele- 



ns 



FIG. 137. Owen's original diagram of a typical vertebra, to illustrate 

 his theory of the archetype. [After OWEN.] 



ns, neural spine; s, zygapophysis ; np, neurapophysis ; d, diapophysis; pi, pleura- 

 pophysis; p, parapophysis; hp, haemapophysis; hs, haemal spine; h, haemal canal. 



ments. The neural arch consists of a pair of neurapophyses 

 and a neural spine, and bears a pair of articular processes, the 

 zygapophyses; and in like manner the haemal arch is composed 

 of a pair of hamapophyses, a hcemal spine and a second pair of 

 zygapophyses. Of the lateral pieces the central ones are the 

 pleurapophyses or rib elements, sometimes forming free ribs, 

 and dorsal and ventral to these lie respectively the diapophyses 

 and parapophyses, more occasional elements. 



