GENERAL CHARACTERS OF THE VERTEBRATA. 199 



nizable with great difficulty, as its parts are generally much 

 modified ; but a good example may be obtained in the human 

 chest. Here, attached to the front of the vertebrae, we find a 

 series of bony arches, known as the ribs (r), followed by a 

 series of cartilaginous pieces of a similar shape, termed the 

 " costal cartilages " (p), the whole united in front by a central 

 bone, known as the breastbone or " sternum " (). 



FIG. 95. Skeleton of the Beaver (Castor fiber), showing the regions of the vertebra 

 column, c Cervical region, or region of the neck ; d Dorsal region, or region of the 

 back ; b Lumbar region, or region of the loins ; s Sacrum ; t Caudal region, or region 

 of the tail. 



As a general rule, among the higher Vertebrates, the fol- 

 lowing regions may be recognized in the vertebral column : 

 Firstly, the cervical region (Fig. 95, c), comprising a variable 

 number of vertebras, which constitute the neck, and immedi- 

 ately follow the head. Secondly, the cervical region is suc- 

 ceeded by a variable number of vertebrae which usually carry 

 ribs, and are known as the dorsal vertebrae (d\ or vertebrae 

 of the back. Thirdly, come certain vertebrae which constitute 

 the lumbar region (0), or the region of the loins. Fourthly, 

 there usually follows a series of vertebrae which are immova- 

 bly united together to form a single bone, which is termed the 

 sacrum (s). Lastly, there comes a variable series of vertebras 



