VERTEBEAL COLUMN 117 



tively thick in the remaining thoracic, the lumbar, and most of the 

 vertebrae of the tail. 



In works on Comparative Osteology the student will find a system 

 of nomenclature for the parts of a vertebra which differs from that 

 employed in human anatomy, and from that given in the preceding 

 pages. This system was introduced by Richard Owen in his attempt 

 to construct an archetypal or primitive vertebra. In it the processes 

 are termed apophyses, and their differences in position and function 

 are indicated by different Greek prefixes. The relation at present 

 between the two systems may be shown as follows : 



Neurapophysis = spinous process. 



Prezygapophysis l = cephalic articular process. 



Postzygapophysis = caudal articular process. 



Metapophysis 2 = mammillary process. 



Anapophysis 3 = accessory process. 



Diapophysis 4 = a transverse process articulating with the tubercle 

 of the rib ; hence the transverse element of the cervical transverse 

 process. 



Parapophysis 5 = a transverse process from the body of a vertebra 

 articulating with the head of the rib ; hence the proximal part of 

 the costal element of the cervical transverse process. 



Pleurapophysis 6 = a rib, or an ossification which is rib-like in 

 position, as the distal part of the costal element of the cervical trans- 

 verse process, or the tip of the lumbar transverse process. 



Epapophysis 7 = ridge on dorsal surface of body. 



Hypapophysis 8 = ridge on ventral surface. 



Hyperapophysis 9 = tubercle on cervical lamina 3 . 



Hsemapophysis 10 = chevron bone. 



VAKIATIONS IN VERTEBRAE. 



The variations in the vertebra may be classified as (1) Variations 

 in size, and in degree of development of their parts. (2) Variations 

 in the number in any region. (3) Malformations due to defective 

 development, 



1 Zygon, a yoke. 2 Meta, after, beyond. 3 Ana, backward. 



* Dia, across, between. 5 Para, beside. 6 Pleura, rib. 



7 Epi, upon. B Ili/po, under. 9 Hyper, above. 

 10 Hcema, blood. 



