VERTEBEAL COLUMN. 397 



thoracic and abdominal portions of the column, owing to the 

 fusion of their component vertebrffi ; (3) the great length of 

 that portion of the vertebral column with which the pelvis is 

 connected ; (4) the small number of the caudal vertebrae, and 

 the fusion of the posterior ones to form the pygostyle ; (5) the 

 absence of epiphyses. 



The vertebral column may be divided into cervical, 

 thoracic, sacral, and caudal regions : the boundaries between 

 these being ill defined, and the sacral portion being further 

 divisible into three sub-sections. 



1. The cervical vertebrae. The boundary between cervical 

 and thoracic vertebrae is an arbitrary one, of no mor- 

 phological value, and is not easy to determine in 

 the fowl. It is usual to count as the first thoracic 

 vertebra the most anterior one which bears a rib 

 articulating with the sternum, and to name all the 

 vertebrae in front of this one cervical. Beckoned in 

 this way there are sixteen cervical vertebrae, the two 

 hindmost of which bear well- developed and movably 

 articulated ribs, which, however, do not reach the 

 sternum. 



In the following description the vertebral column 

 is supposed to be placed horizontally. 



a, A typical cervical vertebra : any one from the sixth 

 to the tenth. 



The parts of the vertebra are the same as in the 

 rabbit, except thatthere are no terminal epiphyses. 

 The chief peculiarities are the following : — 

 i. The vertebra is very long and light, as compared 



with the cervical vertebra of a rabbit, 

 ii. The centrum is slender. The terminal arti- 

 cular surfaces are saddle-shaped, the anterior 

 one being convex from above downwards, 

 and concave from side to side ; while the 

 posterior surface, which is larger and more 

 prominent, is concave from above downwards, 

 and convex from side to side. These saddle- 



