no THE RIBS. [CHAP. 



The portion of the rib between the head and the tubercle 

 is called the neck ; it is wanting in the last two ribs, in which 

 the two attachments are blended. The greatest point of curva- 

 ture on the external surface of the rib is called the angle. 



Each vertebral rib has a main centre of ossification and 

 two epiphyses, one for the head and (except in the last 

 two) one for the tubercle. 



The sternal ribs generally remain cartilaginous throughout 

 life, being only partially ossified by endostosis in old age or 

 under abnormal conditions. They are not distinctly sepa- 

 rated from the vertebral ribs except by their difference of 

 structure ; but synovial joints are (except in the first) inter- 

 posed between their inferior extremities and the sternum. 



Among the higher Simiina the ribs do not differ very 

 notably from those of Man, except in number; but in the 

 lower forms, and especially in the Lemitrina, they more 

 resemble those of the Carnivora. Among the Old World 

 Monkeys the number varies from n to 13 pairs. The 

 Gorilla, Chimpanzee (Troglodytes} and Gibbon (Ifylobates) 

 have 13, and the Orang (Simia] 12. In the American 

 Monkeys there are from 12 to 15 pairs; in the Lemurs 

 from 12 to 17 pairs. 



In the most typical forms of CARNIVORA the vertebral 

 ribs are comparatively slender, subcylindrical, and little 

 curved. The most anterior espjcially are short and straight, 

 the thorax being thus more compressed in front than it is in 

 Man and the higher Primates. The sternal ribs (see Fig. 

 33, p. 94) are long, slender, have a feeble granular ossifica- 

 tion, and are not otherwise segmented off from the vertebral 

 ribs. In all the Fdidcc and Canidce- there are 13 pairs, in 

 the Viverridcc 13 or 14, in the Hyienidtc 14 or 15, in the 

 Mustdidic 14 to 1 6, in the Procyonid<z 14, in the Ursidtc 14 

 or 15, in the Pinnipcdia 14 or 15, 



