clined to consider him as a model example of our third type. The most essential point of his character and the secret of it seems to lie in the fact, that after utilizing the infantile activity of curiosity in the service of sexual interest he was able to sublimate the greater part of his libido into the impulse of investigation. But to be sure the proof of this conception is not easy to produce. To do this we would have to have an insight into the psychic development of his first childhood years, and it seems foolish to hope for such material when the reports concerning his life are so meager and so uncertain; and moreover, when we deal with information which even persons of our own generation withdraw from the attention of the observer.
We know very little concerning Leonardo's youth. He was born in 1452 in the little city of Vinci between Florence and Empoli; he was an illegitimate child which was surely not considered a great popular stain in that time. His father was Ser Piero da Vinci, a notary and descendant of notaries and farmers, who took their name from the place Vinci; his mother,
