198 



VERTEBRATE ANIMALS. 



FIG. 94. A. Vertebra (lumbar) of the whale, c Centrum or body; n Neural arches; 

 8 Spinous process ; a Articular process ; d Transverse processes. B. Thoracic segment 

 or vertebra, c Centrum of vertebra ; n Neural arches, enclosing the canal for the spinal 

 cord ; e Spinous process ; r Eibs ; p Costal cartilages ; b Breastbone or sternum. (After 

 Owen.) 



umn great flexibility. - From the back of the body of the ver- 

 tebra 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 (n) are called the 

 " neural " arches. From the point where the neural arches 

 unite that is to say, from the back of the neural canal pro- 

 ceeds a long process, sometimes cleft at its extremity, termed 

 the "spinous process" (s). Springing also from each neural 

 arch is a second shorter process (a) termed the " articular pro- 

 cess," since by means of these, as well as by the bodies, the 

 vertebrae 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 (d) 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 

 technical 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 vertebra, and which is known as the " haemal " arch, as 

 it includes and protects the principal organs of the blood cir- 

 culation (Fig. 94, B). This second arch is often only recog- 



