894 



D'ARCY WENTWORTH THOMPSON ON 



curved lines of intersection, which form a new system of co-ordinates and constitute 

 a simple " projection " of our human skull. The network represented in fig. 63 

 constitutes such a projection of the human skull on what we may call, figuratively 

 speaking, the " plane " of the chimpanzee ; and the full diagram in fig. 64 demon- 

 strates the correspondence. In fig. 65 I have shown the similar deformation in the 

 case -of a baboon, and it is obvious that the transformation is of precisely the same 

 order, and differs only in an increased intensity or degree of deformation. 



In both dimensions, as we pass from above downwards and from behind forwards, 

 the corresponding areas of the network are seen to increase in a gradual and approxi- 



Fig. 64. — Skull of chimpanzee. 



Fig. 65.— Skull of baboon. 



mately logarithmic order in the lower as compared with the higher type of skull ; 

 and, in short, it becomes at once manifest that the modifications of jaws, braincase, 

 and the regions between are all portions of one continuous and integral process. It 

 is of course easy to draw the inverse diagrams, by which the Cartesian co-ordinates 

 of the ape are transformed into curvilinear and non-equidistant co-ordinates in man. 

 From this comparison of the gorilla's or chimpanzee's with the human skull we 

 realise that an inherent weakness underlies the anthropologist's method of comparing 

 skulls l>v reference to a small number of axes. The most important of these arc the 

 "facial" and " basicranial" axes, which include between them the "facial angle." 

 But it is, in the first place, evident that these axes are merely the principal axes of 

 ;i svstem of co-ordinates, and that their restricted and isolated use neglects all that 

 can be learned from the fillino- in of the rest of the co-ordinate network. And, in 



