102 



VERTEBRATA. 



and is known as the " body " or " centrum " (c). From the 

 upper or posterior surface of the centrum spring two bony 

 arches (n, n), which are called the "neural arches" or "neura- 

 pophyses," because they form with the body a canal — the 

 " neural canal " — which encloses the spinal cord. From the 

 point where the neural arches meet behind, there is usually 

 developed a longer or shorter spine, which is termed the 

 " spinous process " or " neural spine " (s). From the neural 

 arches there are also developed in the typical vertebra two 

 processes (a, a), which are known as the " articular " pro- 

 cesses, or " zygapophyses." The vertebrte are united to one 

 another partly by these, but to a greater extent by the 

 bodies or " centra." From the sides of the vertebral body, 

 at the point of junction with the neural arches, there proceed 

 two lateral processes {d, d), which are known as the " trans- 

 verse processes." 



Fig. 4S0. — A, Lumbar vertebra of a Wliale : c, Body or centrum ; n, n. Neural arches ; 

 s. Neural spine ; a, a, Articular j>roeesses ; d, d, Transverse processes, b, Diagram of a tho- 

 racic vertebra : c, Centrum ; n, n, Neural arches enclosing the neural canal ; s. Neural spine ; 

 r, r. Ribs, assisting in the formation of the h»mal arch ; p, p, Costal cartilages ; li. Sternum, 

 with hsemal spine. (After Owen.) 



These elements form the vertebra of the human anato- 

 mist, but the " vertebra " of the transcendental anatomist is 

 completed by a second arch which is placed beneath the 

 body of the vertebra, and which is called the " ha?mal " 

 arch, as it includes and protects the main organs of the 

 circulation. This second arch is often only recognisable 

 with great difficulty, as its parts are generally much modi- 



