238 



THE ANATOMY OF VERTEBRATED ANIMALS. 



of the vertebra for the capitulum of the rib, while the upper 

 part of the neural arch gives off a more elongated transverse 

 process for the tuberculum. Thus the transverse processes of 

 all the dorsal vertebrae of a bird resemble those of the two an- 

 terior dorsals of a crocodile, and no part of the vertebral col- 

 umn of a bird presents transverse processes with a step for 

 head of the rib, like those of the great majority of the vertebrae 

 of Crocodllia, Dlnosauria^ Dicynodontia^ and JPterosauria. 



The discrimination of the proper lumbar, sacral, and ante- 

 rior caudal vertebrae, in the anchvlosed mass which constitutes 

 the so-called " sacrum " of a bird, is a matter of considerable 



Pig. 80. — ^The "Sacrum" of a Chick, dl., dorso-lumhar ; s., sacral; c, caudal vertebrsE,. 



difficulty. The general arrangement is as follows : The most 

 anterior lumbar vertebra has a broad transverse process, which 

 corresponds in form and position with the tubercular trans- 

 verse process of the last dorsal. In the succeeding lumbar 

 vertebrae tliis process extends downward ; and, in the hinder- 

 most, it is continued from the centrum, as well as from the 

 arch of the vertebra, and forms a broad mass which abuts 

 against the ilium.* This process might well be taken for a 

 sacral rib, and its vertebra for the proper sacral vertebra. 

 But, in the first place, I find no distinct ossification in it ; and, 

 secondly, the nerves which issue from the intervertebral fora- 

 mina in front of and behind this vertebra enter into the lum- 

 bar plexus, which gives origin to the crural and obturator 

 nerves, and not into the sacral plexus, which is the product of 

 the nerves which issue from the intervertebral foramina of the 

 proper sacral vertebrae in other Vertehrata. Behind the last 

 lumbar vertebra follow, at most, five vertebrae, which have no 

 ribs, but their arches give off horizontal, lamellar, transverse 

 processes, which unite with the ilia. The nerves which issue 

 from the intervertebral foramina of these vertebra3 unite to 



* It would be more proper to say that ossification extends into it from tho 

 centrum as well as from the neural arch. The process, like other processes, 

 exists before the centrum is dilferentiated from the arch by ossification. 



