tions it has not been wholly unprofitable. It has enabled us to trace a number of conditions which, even if they cannot always be described as factors of the genius constitution, clearly appear among the influences highly favorable to its development. Such a condition seems to be the great reproductive activity of the parents, the child destined to attain intellectual eminence in many cases alone surviving. The fact of being either the youngest or the eldest child is a condition favorable for subsequent intellectual eminence; and I may add that I could refer to numerous recent instances of large families, in which the eldest and the youngest, but no other members, have attained intellectual distinction. We have further seen that there is a tendency for children who develop genius to be of feeble health, or otherwise disabled, during the period of physical development. It is easy to see the significance of this influence which by its unfavorable effects on the development of the limbs—an effect not exerted on the head which may thus remain relatively large—leaves an unusual surplus of energy to be used in other directions; at the same time the child, who is thus deprived of the ordinary occupations of childhood, is thrown back on to more solitary and more intellectual pursuits. The clumsiness and other muscular incoordinations which we have found to be prevalent—while there is good reason to believe that they are of congenital origin—cooperate to the same end. Again, it is easy to see how the shock of contact with a strange and novel environment, which we have proved to be so frequent, acts as a most powerful stimulant to the nascent intellectual aptitudes. It is possible to take a number of other common peculiarities in the course of the development of genius and to show how they either serve to inhibit the growth of genius along unfruitful lines or to further it along fruitful lines.
Such an investigation as the present is far from enabling us to state definitely all the determining factors of genius, or even all the conditions required for its development. It suggests that they are really very numerous and that genius is the happy result of a combination of many concomitant circumstances, though some of the prenatal group of circumstances must remain largely outside our ken. We are entitled to believe that the factors of genius include the nature of the various stocks meeting together in the individual and the manner of their combination, the avocations of the parents, the circumstances attending conception, pregnancy and birth, the early environment and all the manifold influences to which the child is subjected from infancy to youth. The precise weight and value of these manifold circumstances in the production of genius it must be left to later investigators to determine.
