GENERAL CHARACTERS OF THE VERTEBRATA. 219 
nical names which can be employed for them in all animals 
alike. The nature of this work, however, will not allow of the 
introduction of these here. 
In the typical vertebra the segment is completed by a second 
arch, which is placed in front of or beneath the body of the ver- 
tebra, and which is known as the “ hamal” arch, as it includes 
and protects the principal organs of the blood-circulation (fig. 
116, B). 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. Here, attached 
Fig. 117.—Skeleton of the Beaver (Castor filer), showing the regions of the verte- 
bral column. c¢ Cervical region, or region of the neck; d@ Dorsal region, or 
region of the back; 4 Lumbar region, or region of the loins; s» Sacrum; 
t Caudal region, or region of the tail. 
to the front of the vertebra, we find a series of bony arches, 
known as the ribs (7), followed by a series of cartilaginous pieces 
of a similar shape, termed the “ costal cartilages” (4), the whole 
united in front by a central bone, known as the breastbone or 
“ sternum” (6). 
As a general rule, amongst the higher Vertebrates, the follow- 
ing vegions may be recognised in the vertebral column : Firstly, 
