33 2 



THE ANIMALS AND MAN 



(fig. 167). Each of the first seven ribs is attached to the 

 sternum or breast bone by a rod of cartilage. The carti- 

 laginous ends of the next three join with the cartilage of the 

 seventh, while the remaining two are the so-called floating 

 ribs, joined only to the vertebral column (figs. 166 A, and 159). 

 The skull (fig. 1 68) .--The skull is formed by the union 



V 



N 



1M 







FIG. 168. A side view of the skull. F, frontal bone; P, parietal; S, 

 sphenoid; T, temporal; N, nasal; M, malar; S M., superior maxilla; 

 I M., inferior maxilla; O, occipital. (After Martin.) 



of the cranial and facial bones. They are so fitted to one 

 another that they completely enclose the brain. Some are 

 perforated to admit the passage of nerves and blood-vessels. 

 The sphenoids and ethnoid bones form the floor of the cra- 

 nium. The occipital bone (O) lies at the back of the skull. 

 The temporal bones (T) form the sides. Within the tem- 

 poral bones are embedded the channels of the inner ear. 



