in.] GENERAL CHARACTERS. 19 



vertebra in a large series of animals, some further light will 

 be thrown on the subject ; but at present it does not appear 

 that there is that uniformity in the plan of construction of 

 all vertebrae which has often been supposed, and definitions 

 of the different parts applicable in every case have not yet 

 been arrived at, and it may even be doubted whether this 

 will ever be possible. 



m 



FIG. 3. Anterior surface of the lumbar vertebra of Hare (Lef>its tiniidns). s spinou 

 process ; m metapophysis ; az anterior zygapophysis ; t transverse process ; 

 hypapophysis. 



The principal processes commonly met with are as 

 follows :- 



1. From the middle of the upper part of the arch, a process 

 (Fig. 3, s) generally single, but sometimes bifid at the end, 

 grows out vertically. This is the spinous process ; or neural 

 spine already mentioned ; about its homology in different 

 vertebras there never can be any question. It may, however, 

 be completely absent when the arch is round or smooth 

 above, as in the cervical region in some animals ; on the 

 other hand, it may grow out into a very long conspicuous 

 rod of bone, as in the anterior dorsal region of others. 



2. Occasionally a process grows in the median line from 

 the under-surface of the body. This may be single and long 

 and slender, as in the anterior lumbar vertebrae of the Hare 



C 2 



