278 



THE ANATOMY OF VERTEBEATED ANIMALS. 



The discrimination of tlie proper lumbar, sacral and 

 anterior caudal vertebrae, in the ankylosed mass which consti- 

 tutes the so-called " saciiim" of a bird, is a matter of consider- 



Fis. 80. 



a'Z s 



Fig. 80. — The "Sacrum" of a Chick, dl., dorso-lumbar ; s., sacral; 

 c, caudal vertebrae. 



able 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 transverse process of the last dorsal. In the 

 succeeding lumbar vertebras this process extends down- 

 wards; and, in the hindermost, 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 ver- 

 tebra 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 foramina in 

 front of and behind this vertebra enter iuto the lumbar 

 plexus, which gives origin to the craral and obtiirator nerves, 

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

 nei-ves which issue from the intervertebral foramina of the 

 proper sacral vertebrse in other Vertehrata. Behind the last 

 lumbar vertebra follow, at most, five vertebrae, which have 

 no ribs, bu.t their arches give off horizontal, lamellar, trans- 

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

 issue from the intervertebral foramina of these vertebrae 



* It would be more proper to 

 say that cssi6cation extends into 

 it from the centrum as well as 

 from the neural arch. The pro 



cess, like other processes, exists 

 before the centrum is differen- 

 tiated from the arch by ossifi- 

 cation. 



