BOAS] HANDBOOK OF AMERICAN INDIAN LANGUAGES 57 



for the reason that these three peoples have certain psychical traits 

 in common which are not shared in by other American tribes. 



It seems certainly admissible to assume slight differences in the 

 psychical make-up among groups of a race which are different in re- 

 gard to their physical type. If we can prove by means of anatom- 

 ical investigations that the bodily form, and with it the nervous 

 system and the brain of one part of a race show dift'erences from 

 the analogous traits of another part of the race, it seems justifiable 

 to conclude that the physical differentiation may be accompanied 

 by psychic differences. It must, however, be borne in mind that 

 the extent of physical difference is always exceedingly slight, and 

 that, within the limits of each geographical type, variations are 

 found which are great as compared to the total differences between 

 the averages of the types. To use a diagram: 



I ^ \ 1 



b <i c 



I \ —\, 



¥ a' c' 



If a represents the middle point of one type and h and c its extremes, 

 a' the average of another type and h' and c' its extremes, and if 

 these types are so placed, one over the other, that types in the second 

 series correspond to those in the first series vertically over them, 

 then it will be seen that the bulk of the population of the two 

 types will very well coincide, while only the extremes will be more 

 frequent in the one group than in the other. That is to say, the 

 physical difference is not a difference in kind, but a difference 

 more or less in degree, and a considerable overlapping of the types 

 necessarily takes place. 



If this is true in regard to the physical type, antl if, furthermore, 

 the difference in psychical types is inferred only from the observed 

 differences of the physical types, then we must assume that the same 

 kind of overlapping will take place in the psycliical types. The 

 differences with which we are dealing can, therefore, be only very 

 slight, and it seems hardly likely that these slight differences could 

 lead to radically diverse results. 



As a matter of fact, the proof which has been given before,^ that 

 the same languages may be spoken by entirely distinct types, shows 

 clearly how slight the effect of difference in anatomical type upon 



1 See p. 9. 



