08 



THE BONES. 



groove for ligamentous insertion ; it is isolated from the tuberosity by a 

 narrow part, named the neck, which exhibits a rugged fossa for the implanta- 

 tion of a ligament. The second, situated behind the head, and smaller than 

 it, is provided with imprints on its margin, and presents an almost flat 

 diarthrodial facet at the summit. Each rib articulates by its head and 

 tuberosity with two dorsal vertebras ; the head is received into the inter- 

 Fig. 33. 



TYPICAL RIBS OF THE HORSE. 



A, Inner face of the fifth sternal rib ; B, External face of the first asternal rib. 

 1, Head of the rib ; 2, Its fissure ; 3, Neck ; 4, Tuberosity ; 5, Articular facet ; 



6, Scabrous fossa for the insertion of the interosseons costo-transverse ligament ; 



7, Groove on the external face ; 8, Vasculo-nervous groove of the posterior 

 border ; 9, Prolonging cartilage ; 10, A, Articular tuberosity for union with the 

 sternum. 



vertebral articular cavity ; the tuberosity corresponds, by its facet, to the 

 transverse process of the posterior vertebra. 



The inferior extremity is tuberous and excavated by a shallow cavity, 

 irregular at the bottom, for the reception of the upper end of the costal 

 cartilage. 



Structure and development. The ribs are very spongy bones, especially 



