Some Considerations respeciing the Parietal Bone. 



325 



in the first named birds or to the more forcible operations engaged 

 on by the beaks of the rasores (v. Cursores). The interparietal should 

 be regarded apparently as an occipital segment (Meckel). Indeed, at 

 an early age, it is frequently joined to the hind-head bone. . 



The inflated brain in some of the mammalian orders causes so much 

 extension of the parietal, and frontal bones, that it is difficult or 

 impossible to estimate the value of the nervous system beneath in 



Fig. 15. 

 Galhrs (Var.) 



Fig. 16. 

 Struthio. 



producing the increased size as compared with the influence of 

 muscular activity and the impulses conveyed from without through the 

 suturai surfaces. The parietal is in contact with the occipital bone and 

 must be influenced by vertebral impulses, and along the maxillae, 

 jugals, temporals, and sphenoids, impulses travel that affect the nutri- 

 tion of the frontals and parietals. This bone seems a more accurate 

 index of brain inflation in the higher groups, where it becomes not 

 only large and square but arched. Whatever is the origin of this 



