218 VERTEBRATE ANIMALS. 
vertebra (fig. 116, A) consists of a central portion known as the 
“body,” or “centrum” (c), placed immediately below the spinal 
cord, and giving origin to certain “processes.” The ends of the 
bodies of the vertebrze are all united together in different ways, 
so as to give the column great flexibility. From the back of 
the body of the vertebra proceed two bony arches which unite 
behind and thus form with the centrum a bony canal in which 
the spinal cord is contained. For this reason these arches (7) 
are called the “neural” arches. From the point where the 
neural arches unite—that is to say, from the back of the neural 
canal—proceeds a long process, sometimes cleft at its extremity, 
' Fig. 116.—A. Vertebra (lumbar) of the whale: ¢ Centrum or body; z Neural 
arches ; sSpinous process ; a Articular process ; d Transverse processes. B. 
Thoracic segments or vertebra: ¢ Centrum of vertebra; 2 Neural arches, 
enclosing the canal for the spinal cord; s Spinous process; ~ Ribs; » Costal 
cartilages ;  Breastbone, or sternum. (After Owen.) 
termed the “spinous process” (s). Springing also from each 
neural arch is a second shorter process (a) termed the “ articular 
process,” since by means of these, as well as by the bodies, the 
vertebree are jointed or “articulated” together. Also arising 
from the neural arches at their junction with the body of the 
vertebra, there may be two lateral processes (@) which are called 
“transverse processes.” This is the ordinary structure of the 
vertebra of a Mammal, and the names here used are those 
applied to the parts of the vertebra in human anatomy. In 
philosophical anatomy, however, these parts have proper tech- 
