90 



EVOLUTION, GENETICS, AND EUGENICS 



second or the third molar of man presents five cusps — in the one case 

 following the chimpanzee, in the other the gorilla. These latter varia- 

 tions, therefore, may fairly be regarded as reversionary. For these 

 facts I am indebted to the kindness of Mr. C. S. Tomes. 



10. Perforations of the humerus. — The peculiarities which we 

 have to notice under this heading are two in number. First, the 

 supra-condyloid foramen is a normal feature in some of the lower 

 Quadrumana (Fig. 24), where it gives passage to the great nerve of 



N AT. SIZE 



OK.A.N"G- 



/<\AjS. 



Fig. 23. — Molar teeth of lower jaw in gorilla, orang, and man. Drawn from 

 nature, nat. size. (From Romanes.) 



the forearm, and often also to the great artery. In man, however, 

 it is not a normal feature. Yet it occurs in a small percentage of 

 cases — viz., according to Sir W. Turner, in about one per cent, and 

 therefore is regarded by Darwin as a vestigial character. Secondly, 

 there is inter-condyloid foramen, which is also situated near the lower 

 end of the humerus, but more in the middle of the bone. This occurs, 

 but not constantly, in apes, and also in the human species. From 

 the fact that it does so much more frequently in the bones of ancient 

 — and also of some savage — races of mankind (viz. in 20 to 30 per cent 

 of cases), Darwin is disposed to regard it also as a vestigial feature. 



