Let us expressly emphasize that we have never considered Leonardo as a neurotic or as a "nervous person" in the sense of this awkward term. Whoever takes it amiss that we should even dare apply to him viewpoints gained from pathology, still clings to prejudices which we have at present justly given up. We no longer believe that health and disease, normal and nervous, are sharply distinguished from each other, and that neurotic traits must be judged as proof of general inferiority. We know to-day that neurotic symptoms are substitutive formations for certain repressive acts which have to be brought about in the course of our development from the child to the cultural man, that we all produce such substitutive formations, and that only the amount, intensity, and distribution of these substitutive formations justify the practical conception of illness and the conclusion of constitutional inferiority. Following the slight signs in Leonardo's personality we would place him near that neurotic type which we designate as the "compulsive type," and we would compare his investigation with the "reasoning mania" of neurotics, and his inhibitions with the so-called "abulias" of the latter. The object of our work was to explain the inhibitions in Leonardo's sexual life and in his artistic activity. For this purpose we shall now sum up what we could discover concerning the course of his psychic development. We were unable to gain any knowledge about his hereditary factors, on the other hand we recognize that the accidental circumstances of his childhood produced a far reaching disturbing effect. His illegitimate birth deprived him of the influence of a father until perhaps his fifth year, and left him to the tender seduction of a mother whose only consolation he was. Having been kissed by her into sexual prematurity, he surely must have entered into a phase of infantile sexual activity of which only one single manifestation was definitely evinced, namely, the intensity of his infantile sexual investigation. The impulse for looking and inquisitiveness were most strongly stimulated by his impressions from early childhood; the enormous mouth-zone received its accentuation which it had never given up. From his later contrasting behavior, as the exaggerated sympathy for animals, we can conclude that this infantile period did not lack in strong sadistic traits.