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232   Life and Letters of Francis Galton

intraracial groups markedly differentiated in mental characters do not give markedly differentiated composite photographs, should not be considered merely negative and disappointing. It should have been interpreted as a most valuable anthropometric result, namely that mental characters are not highly correlated with external physical characters. That conclusion is confirmed by modern research on quite different lines; there is little or no correlation between human mentality and external anthropometric characters. I am fully aware that this result cuts directly at the whole of popular belief in physiognomy and phrenology and of the old anatomical ideas of craniometry. But this principle statistically demonstrated will stand, and composite photographs pointed at an earlier date in the same direction. The characters of the mind, the workings of the brain depend in the main upon commissures and linkages, matters of a far more subtle nature than the shape of the brain case. Whether the efficiency of the mind is more closely correlated with -the physiological processes of the body, i.e. with its dynamic qualities, than with its static properties is another question, still sub judice. But one fundamental result of Galton's introduction of psychometry into anthropometric measurements has been to demonstrate the very small relation of mentality to external bodily characters. It is from this standpoint that Galton's composite photographs did and may still do useful work.

It may be argued that the American Indian, the Negro and the Western European have as markedly divergent and individual mental characters as they have divergent and individual physical characters (see our p. 81), and that both are inherited within these races of men. That there is interracial correlation between mental and physical attributes goes without saying as long as races are inbred. Each race simply transmits its own mentality and its own physique, but that is no proof of a high intraracial correlation between the two. Any geneticist knows how relatively easy it is to separate the mental and superficial characters of one breed by crossing it with another, much easier than it is to combine the forelimbs of one breed with the hindlimbs of a second ; the simple reason being the relatively high correlation of the two members'. Goring has shown' that the average criminal is not differentiated markedly from the normal man by his physical characters; in England at any rate he is not the physically anomalous being of the Lombrosian school of criminologists.

The-non-differentiation in a markedly significant manner of the composites of groups selected by mental characters contained a fundamental scientific fact, which has had to wait many years for us to grasp its full significance, and will possibly have to wait more years still for its general popular recognition.

1 In breeding several hundred dogs from crosses of Pekingese and Pommeranians, there has only been one instance in which it might be supposed that a Pekingese forelimb was combined with a Pommeranian hindlimb; but it has been quite possible to obtain a pointed muzzle and chocolate coat combined with the strong mental individuality of the Pekingese. I feel certain that a differentiation by mental qualities of our hybrids would not on composite photography reproduce Pommeranian and Pekingese external characters.

' The English Convict, A Statistical Study. By Charles Goring, M.D., H.M. Stationery Office.