Ill VARIATIONS: HUMAN SKULLS 197 



discern, between the lowest and the highest forms 

 of the human cranium anything answering, in 

 however slight a degree, to this revolution of the 

 side and roof bones of the skull upon the basi- 

 cranial axis observed upon so great a scale in the 

 mammalian series ? Numerous observations lead 

 me to believe that we must answer this question 

 in the affirmative. 



The diagrams in Figure 30 are reduced from 

 very carefully made diagrams of sections of four 

 skulls, two round and orthognathous, two long and 

 prognathous, taken longitudinally and vertically, 

 through the middle. The sectional diagrams have 

 then been superimposed, in such a manner, that 

 the basal axes of the skulls coincide by theii 

 anterior ends, and in their direction. The devia- 

 tions of the rest of the contours (which represent 

 the interior of the skulls only) show the differ- 

 ences of the skulls from one another, when these 

 axes are regarded as relatively fixed lines. 



The dark contours are those of an Australian 

 and of a Negro skull: the light contours are 

 those of a Tartar skull, in the Museum of the 

 Royal College of Surgeons; and of a well 

 developed round skull from a cemetery in 

 Constantinople, of uncertain race, in my own 

 possession. 



It appears, at once, from these views, that the 

 prognathous skulls, so far as their jaws are con- 

 cerned, do really differ from the orthognathous in 



