THE TIGEON. 183 



II. Notice, first of all, the general composition of the 

 skeleton : it consists of: 



1. The vertebral column, distinguishable into (a) 

 thirteen or fourteen cervical vertebrae, forming the 

 skeleton of the neck, and the last two of them bearing well- 

 developed ribs, which do not unite with the sternum ; (b) 

 the four anterior thoracic vertebras, all united with one 

 another and bearing ribs which articulate with the sternum ; 

 (c) the compound sacrum, consisting of several vertebras 

 ankylosed together, and giving attachment to the pelvis ; of 

 these ankylosed vertebras the first is thoracic, bearing ribs 

 which unite with the sternum, the next two or three are 

 lumbar, the next three or four sacral, and the remaining 

 six caudal (d) the free caudal vertebrae, about six in 

 number; and (e) the pygostyle or ploughshare bone, a 

 laterally compressed plate, forming the posterior termination 

 of the vertebral column. 



2. The skull, consisting of (a) the brain-case and upper 

 jaw; (b) the lower jaw or mandible ; and (<) the hyoid 

 or tongue-bone. 



3. The sternum, a broad, keeled plate, giving attach- 

 ment to the five pairs of thoracic ribs. 



4. The skeleton of the wings or fore-limbs, articulat- 

 ing with the shoulder-girdle, which consists of two bones 

 on each side, the ventral one articulating with the sternum, 

 and connected with its fellow by the U-shaped furcula or 

 merrythought. 



5. The skeleton of the hind-limbs or legs, articulating 

 with the pelvis or hip-girdle, the two halves of which are, 

 in the adult, firmly united with the sacrum. 



III. Examine the last cervical vertebra, and make out 

 the following parts : 



6. The centrum or body of the vertebra, elongated 



