132 ZOOTOMY. 



their maximum size in the anterior thoracic region, where 

 they are united to the steriium (§ 4), and undergo a gradual 

 reduction in size in the posterior thoracico-lumbar region. 



4. The sternum and shoulder-girdle, together forming 

 an inverted arch of mingled bone and cartilage in the 

 anterior thoracic region, to the vertebrae of which the sternum 

 is united by ribs. 



5. The fore-limb, articulated to the shoulder-girdle. 



6. The pelvis or hip-girdle, attached to the sacral 

 vertebrae. 



7. The hind-limbs, articulated to the pelvis. 



III. Observe the following points in the vertebral 

 column : 



8. The characters of one of the anterior thoracic vertebras : 

 it consists of a ventral cylindrical portion, the centrum, 

 concave in front, convex behind (proccelous), from which 

 rises up on each side a vertical plate, the neural process 

 or neurapophysis : this, uniting with its fellow in the 

 middle dorsal line, incloses the neural arch, which is 

 produced at its apex into a short, backwardly directed 

 neural spine. 



9. The zygapophyses, horizontal processes, two anterior, 

 given off one from each side of the anterior border of the 

 neural arch, and two posterior, similarly related to its posterior 

 border : the anterior pair bear smooth articular facets on 

 their dorsal surfaces, the posterior pair on their ventral 

 surfaces. 



10. The capitular facets, one on each side of the 

 vertebra, at the junction of the centrum and neural arch 

 and close to the anterior border of the latter : they serve for 

 the articulation of ribs. 



11. The mode of articulation of successive vertebra;: 

 each fits by the concave anterior face of its centrum against 



