Typhoid is commoner in males; and Moebius lays stress on the fact, which he regards as especially striking, that the difference in the sex-incidence of this disease is manifest even in childhood. As regards colour-blindness, there is a notable preponderance among males, and since we here have to do with a congenital affection, this preponderance is as marked among children as among adults. Many defects of speech also exhibit a notable difference in their sex-incidence. Hermann Gutzmann[21] has shown that in the case of stammerers we find 71 per cent. boys and 29 per cent. girls. I take this opportunity of referring briefly to the fact that, as Max Marcuse[22] reports, certain diseases of the skin exhibit sexual differentiation of type even during childhood. The disseminated cutaneous gangrene of children is far more frequent in girls than it is in boys; Broker, among twelve cases, found ten girls. Alopecia areata, on the other hand, affects both sexes with equal frequency, but affects them at different ages. Whereas during the first years of life girls are more frequently attacked; when the age of twenty is passed, the relation between the sexes in this respect are reversed. Criminological experiences appear also to confirm the notion of an inherited sexual differentiation, in children as well as in adults. According to various statistics, embracing not only the period of childhood, but including as well the period of youth, we learn that girls constitute one-fifth only of the total number of youthful criminals. A number of different explanations have been offered to account for this disproportion. Thus, for instance, attention has been drawn to the fact that a girl's physical weakness renders her incapable of attempting violent assaults upon the person, and this would suffice to explain why it is that girls so rarely commit such crimes. In the case of offences for which bodily strength is less requisite, such as fraud, theft, &c., the number of youthful female offenders is proportionately larger, although here also they are less numerous than males of corresponding age charged with the like offences. It has been asserted that in the law courts girls find more sympathy than boys, and that for this reason the former receive milder sentences than the latter; hence it results that in appearance merely the criminality of girls is less than that of boys. Others, again, refer the differences in respect of criminality between the youthful members of the two sexes to the influences of education and general environment. Morrison,[23] however, maintains that all these influences combined are yet insufficient to account for the great disproportion between the sexes, and insists that there exists in youth as well as in adult life a specific sexual differentiation, based, for the most part, upon biological differences of a mental and physical character. I have referred to these criminological data for the sake of completeness, but