374 



MANUAL OF ZOOLOGY. 



" neurapophyses " 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 " spi- 

 nous 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" processes, or " zyga- 

 pophyses." The vertebrae 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 "transverse processes." (In the typical 



F'g- J 54- A, Lumbar vertebra of a Whale : c Body or centrum ; n Neural arches ; 

 j Neural spine ; a a Articular processes ; d d Transverse processes. B, Diagram of 

 a thoracic vertebra : c Centrum ; n n Neural arches enclosing the neural canal ; 

 ^ Neural spine ; r r Ribs, assisting in the formation of the haemal arch ; // Costal 

 cartilages; b Sternum, with haemal spine. (After Owen.) 



vertebra the transverse processes consist each of two pieces, an 

 anterior piece or " parapophysis," and a posterior piece or 

 " diapophysis.") These elements form the vertebra of the 

 human anatomist, 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 

 " haemal" 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 modified, 

 but a good example may be obtained in the human chest, or 

 in the caudal vertebra of a bony fish. 



The haemal arch in the case of the human thorax (fig. 154, 

 B) is formed by the ribs (r r) and the costal cartilages (p /), 



