22 



OSTEOLOGY. 



roughened for the attachment of the soft intervertebral substance. 

 Its upper or spinal surface is flattened or slightly concave, its 

 inferior surface being convex, and sometimes terminating in a 

 spinous process or prominent ridge. 



The neural arch or ring rises from the supero- lateral surfaces 

 of the body by two processes of bone termed pedicles, from each 

 of which a plate of bone, the lamina, expands and passes inwards, 

 the union of the lamina? in the median line completing the arch, 

 which encloses the neural canal or spinal foramen. 



The notches are excavations in the anterior and posterior sur- 

 faces of each pedicle, so placed that when the vertebra? are in situ 

 the notch in the posterior part of one 

 pedicle corresponds with that in the anterior 

 of the next, the two forming a large open- 

 ing, called the intervertebral foramen, which 

 leads to the neural canal and gives passage 

 to the spinal nerve and blood-vessels. 



Each true vertebra, with the exception 

 of the two anterior cervical ones, has four 

 oblique or articular processes (zygapophyses) 

 on the superior and lateral parts of the 

 arch. The faces of the anterior of these 

 processes are directed upwards and inwards, 

 those of the posterior downwards and out- 

 wards ; as their name implies, they articu- 

 late and form joints with the corresponding 

 processes of contiguous vertebra?. In some 

 of the dorsal and lumbar segments of certain 

 animals, the anterior zygapophyses have 

 pi'ocesses which project above the level of 

 the articular facets; these are the mam- 

 processes (metapophyses). 

 The transverse processes (diapophyses), one on each side, 

 spring from the sides of the body and pedicle, and are projec- 

 tions varying much in size and shape in the different regions. 

 Between the anterior zygapophysis and the metapophysis in some 

 animals there may be another small eminence projecting back- 

 wards (anapophysis). 



The spinous processes are superior and inferior. The superior 

 or neural spine (neurapophysis), formed by the union of the 

 lamina?, and surmounting the centre of the arch, is some- 



FIG. 7. 



Diagramatic transverse sec- 

 tion from the skeleton of a 

 mammalian thorax, showing 

 the chief features of a perfect 

 vertebral segment. 1, Neural 

 spine; 2, Lamina (neurapophy- 

 sis)^, Pedicle; 4, Neural arch; 

 5, Centrum ; 6, Inferior Spine 

 (hypapophysis) ; 7 7, Htemal 

 arch ; 8, Rib (pleurapophysis); 

 9, Costal cartilage (hieina- 

 pophysis) ; 10, Sternebra ; 

 11, Haemal spine. 



