The foregoing sketch will serve to show how vast is the field of life--of normal and not merely abnormal life--more or less infused by auto-erotic phenomena. If, however, we proceed to investigate precisely the exact extent, degree, and significance of such phenomena, we are met by many difficulties. We find, indeed, that no attempts have been made to study auto-erotic phenomena, except as regards the group--a somewhat artificial group, as I have already tried to show--collected under the term "masturbation" while even here such attempts have only been made among abnormal classes of people, or have been conducted in a manner scarcely likely to yield reliable results.[289] Still there is a certain significance in the more careful investigations which have been made to ascertain the precise frequency of masturbation. Berger, an experienced specialist in nervous diseases, concluded, in his _Vorlesungen_, that 99 per cent. of young men and women masturbate occasionally, while the hundredth conceals the truth;[290] and Hermann Cohn appears to accept this statement as generally true in Germany. So high an estimate has, of course, been called in question, and, since it appears to rest on no basis of careful investigation, we need not seriously consider it. It is useless to argue on suppositions; we must cling to our definite evidence, even though it yields figures which are probably below the mark. Rohleder considers that during adolescence at least 95 per cent. of both sexes masturbate, but his figures are not founded on precise investigation.[291] Julian Marcuse, on the basis of his own statistics, concludes that 92 per cent. male individuals have to some extent masturbated in youth. Perhaps, also, weight attaches to the opinion of Dukes, physician to Rugby School, who states that from 90 to 95 per cent. of all boys at boarding school masturbate.[292] Seerley, of Springfield, Mass., found that of 125 academic students only 8 assured him they had never masturbated; while of 347, who answered his questions, 71 denied that they practiced masturbation, which seems to imply that 79 per cent. admitted that they practiced it.[293] Brockman, also in America, among 232 theological students, of the average age of 23½ years and coming from various parts of the United States, found that 132 spontaneously admitted that masturbation was their most serious temptation and all but one of these admitted that he yielded, 69 of them to a considerable extent. This is a proportion of at least 56 per cent., the real proportion being doubtless larger, since no question had been asked as to sexual offenses; 75 practiced masturbation after conversion, and 24 after they had decided to become ministers; only 66 mentioned sexual intercourse as their chief temptation; but altogether sexual temptations outnumbered all others together.[294] Moraglia, who made inquiry of 200 women of the lower class in Italy, found that 120 acknowledged either that they still