First of all, the brains of not all eminent men are unusually large. On the contrary, a few unusually small brains have been found in the series. Furthermore, most of the brain-weights constituting the general series are obtained in anatomical institutes; and the individuals who find their way there are poorly developed, on account of malnutrition and of life under unfavorable circumstances, while the eminent men represent a much better nourished class. As poor nourishment reduces the weight and size of the whole body, it will also reduce the size and weight of the brain. It is not certain, therefore, that the observed difference is entirely due to the higher ability of the eminent men. This may also explain the larger size of the brains of the professional classes as compared to those of unskilled laborers (Ferraira). An additional number of restricting facts must be enumerated. The most important among these is the difference in brain-weight between men and women. When men and women of the same stature are compared, it is found that the brain of woman is much lighter than that of man. Nevertheless the faculty of woman while perhaps qualitatively different from that of man, cannot be deemed to be of an inferior character. 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 do the same work as 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 comparison between male and male.
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.
The reason for a lack of close correlation between brain-weight and mental faculties is not far to seek. The functioning of the brain depends upon the nerve cells and fibres, which do not constitute, by any means, the whole mass of the brain. A brain with many cells and complex connections between the cells may contain less connective tissue than another one of simpler nervous structure. In other words, if there is a close relation between form and ability, it must be looked for rather in the morphological traits of the brain than in its size. A correlation exists between size of brain and number of cells and fibres, but the correlation is weak (Donaldson).
Notwithstanding the numerous attempts that have been made to find structural differences between the brains of different races of man that could be directly interpreted in psychological terms, no conclusive results of any kind have been attained. The status of our present knowledge has been well summed up by Franklin P. Mall, to whose investigation I referred before. He holds, that, on account of the great variability of the individuals constituting each race, racial differences are exceedingly difficult to discover, and that up to the present time none have been found that will endure serious criticism.
We may now sum up the results of our preliminary inquiry. We have found that the unproved assumption of identity of cultural achievement and of mental ability is founded on an error of judgment; that the variations in cultural development can as well be explained by a consideration of the general course of historical events without recourse to the theory of material differences of mental faculty in different races. We have found, furthermore, that a similar error underlies the common assumption that the white race represents physically the highest type of man, but that anatomical and physiological considerations do not support these views.
[1]. For authorities, see note to this page at end of book.
II. INFLUENCE OF ENVIRONMENT UPON HUMAN TYPES
After having seen that the high estimate of our civilization does not necessarily imply that the carriers of this civilization have an anatomical organization superior to that of all other races, we may turn our attention to a closer investigation of the characteristics of different divisions of mankind. It is clear that our investigations cannot be based on vague descriptions of travellers,—who remark upon the enormous digestive organs of primitive man, or on his small size, or on the lack of development of his limbs, or even upon his resemblance to apes,—but on serious studies of anatomical characteristics.