VERTEBRAL COLUMN. 403 



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 vertebras is an arbitrary one, of no 

 morphological 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 that there are no terminal 

 epiphyses. The chief peculiarities are the 

 following : 



Fig. 73. Gallus domesticus. The left half of the skeleton. The skull, 

 vertebral column, and sternum are bisected in the median plane, 

 (c. H. H.) 



A, acetabulum. B, cerebral fossa. CB, cerebellar fossa. CL, clavicle. 

 CO, coracoid. CR, cervical rib. C1 , first cervical vertebra. DE, DM, DO, 

 preaxial, middle, and postaxial digits of the wing. FE, femur. HC, hypo- 

 cleidium. HU, humerus. HY, hyoid. IF, ilio-sciatic foramen. IL, ilium. 

 IS, ischium, l, lacrymal bone. MCu, metacarpal bone of ulnar digit. MN, 

 mandible. MS, metosteon. MT, tarso-metatarsus. MT 1, metatarsal bone, 

 of first digit. N, nasal bone. OP, optic foramen, p, premaxilla. PB, pubes. 

 PL, palatine bone. PY, pygostyle. R, radius. RC, radial carpal bone. S, 

 keel of the sternum. SC, scapula. T, tibio-tarsus. TH 4, fourth thoracic 

 vertebra, y, ulna. UC, ulnar carpal bone. UP, uncinate process of rib. 

 Z, infra-orbital bar. . x . . . 



1 , 2, 3, 4, the first, second, third, and fourth digits of the foot.] 



