These facts were not unknown to old observers. Tassoni, a very original writer, in his _Pensieri Diversi_ (1621) discusses the question: “How it happens to wise fathers to have very foolish children, and to very foolish fathers to have very wise children.” Among the former he mentions the sons of Scipio Africanus, Anthony, Cicero, Agrippa Posthumus, Claudius the son of Drusus, Caligula, of Germanicus, Commodus, of Marcus Aurelius, Lamprocles, of Socrates, Arrhidaeus, of Philip. Among many opinions, more or less extravagant, of learned men of his time, he reports one to the effect that “in great men the vital spirits assemble at the brain to fortify and give vigour to the powers of the intelligence; it happens in consequence that the blood and sperm remain cold and languid, and the children of such men, especially the males, are inclined to stupidity.” _Age of Parents._--This is one of the hereditary influences which often escape from view, and are at present not clearly seen. Marro has shown the great influence of the advanced age of the parents on the intelligence or the insanity of the children. Very great is the number of men of genius, and even of talent, issued from aged fathers: Frederick II., Napoleon I., Sciacci, Bizzozzero, Rochefort, Dumas _père_, A. Jussieu, Balzac, J. Cassini, C. Vernet, Beaconsfield, Horace Walpole, William Pitt, Racine, Adler, Auriac, Béclard, Schopenhauer. From young fathers I have, on the other hand, only found Victor Hugo, De Girardin, Arneth, Barral, Bertillon, Ségur. This influence may explain the longevity of men of genius. _Conception._--De Candolle speaks of the influence which strong passion on the part of the parents at conception may have on the offspring, and recalls the considerable number of bastards of genius. Erasmus boasted that he was not the fruit of wearisome conjugal duty. Isaac Disraeli wrote in his “Memoirs of Toland” that birth outside marriage creates strong and resolute characters. Among illegitimate sons were: Themistocles, Charles Martel, William the Conqueror, the Duke of Berwick whom Montesquieu called the perfect man, Leonardo da Vinci, Boccaccio, A. Dumas, Cardan, D’Alembert, Savage, Prior, De Girardin, La Harpe, Alexander Farnese, Dupanloup.[272] Newton was conceived after his parents had spent two years of forced continence. It will be seen from these and other facts how far we are yet from having exhausted the numerous sources of hereditary genius. Those who recall how many men of genius have been born of consumptive and drunken parents, and who know how these two forms of degeneration are often transformed in the children into moral insanity, will perceive that there can be other hereditary causes of genius which escape ordinary observers, and are, therefore, little known. CHAPTER IV. THE INFLUENCE OF DISEASE ON GENIUS. Spinal diseases--Fevers--Injuries to the head and their relation to genius.