TRUE VERTEBRiE. 21 



Axial Skeleton, 

 vertebral coluio'. 



The vertebral or spinal column may be considered the found- 

 ation of the skeleton, from which all othei" parts proceed. Ex- 

 tending the whole length of the body, it consists -of a series of 

 single bones, termed vertebrce, firmly noited, and it presents 

 a succession of curves ; thus, in the horse, the neck, back, and 

 croup are usually curved, while the loins are nearly straight. 



The vertebral chain may be divided into five regions, exclusive 

 of the cranial portion, which we regard collectively as the skull. 

 These are the cervical, dorsal, lumbar, sacral, and coccygeal — 

 respectively the regions of the neck, back, loins7~ci'dup, an3r"t^l ; 

 and, while all possess certain- points of conformation in common, 

 special peculiarities distinguish the vertebrae of any one region 

 from those of another. 



Vertebrae are either true or false; true vertebrae possess 

 certain typical parts, which they retain throughout the life of 

 the animal, and they never, in health, unite by ossification ; 

 while false vertebrae either do not possess the essential characters 

 of true, or they may become so united. 



TRUE VERTEBRiE. 



A true vertebra consists of a body or centrum, an arch, called 

 the neural arch, notches, and spinous, transverse, and articular 

 processes. The body is the solid block of bone on which all the 

 other parts are built, and which, in quadrupeds, lies below the 

 spinal canal. Its anterior end is convex, and its posterior 

 correspondingly concave, both being discs of compact bone 

 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 laminae in the median line completing the arch, 

 which encloses the neural canal or spinal foramen. 



