"In interpreting these facts, we must ask, Does the increase in the size of the brain prove an increase in faculty? This would seem highly probable and facts may be adduced which speak in favor of this assumption." A number of these, familiar enough, are mentioned, and there follows: "While the force of these arguments must be admitted, a number of restricting facts must be enumerated. The most important among these is the difference in the brain-weight between men and women. When men and women of the same stature are compared it is found that the brain of the woman is much lighter than that of the man. Nevertheless, the faculty of woman is undoubtedly just as high as that of man. This is therefore a case in which smaller brain-weight is accompanied throughout by equal faculty. We conclude from this fact that it is not impossible that the smaller brains of males of other races should not (_sic_) do the same work that is done by the larger brain of the white race. But this comparison is not quite on equal terms, as we may assume that there is a certain structural difference between male and female which causes the difference in size between the sexes, so that comparison between male and female is not the same as a comparison between male and male. We will also remember that, although the brains of eminent men are, on the average, larger than those of the average individual, there are some small brains included in their number." We observe that, the sentence "But this comparison ..." (p. 315) so restricts the foregoing "most important restriction" as to deprive it of all the force it might otherwise have with some. As to eminent men having small brains, to be sure; but eminent men may have small minds also; very extraordinary special endowment does not by any means imply general endowment; not every genius is a good "all-around" man; even as physically some are strong in arm but weak in legs, strong in the chest but weak in the back, and so on. Besides, no one has ever held that mind-power is merely a matter of brain-weight. We hold only that, other things being equal, brain-weight is a fair index of mind-power. Perhaps in no two cases are the other things equal; but in the average of a large number of cases these inequalities are smoothed out; hence it is that we may rely upon the average with no little confidence. "Notwithstanding these restrictions, the increase of the size of the brain in the higher animals, and the lack of development in microcephalic individuals are fundamental facts which make it more than probable that increased size of the brain causes increased faculty, although the relation is not quite as immediate as is often assumed." We ask no greater concession.