In like manner, masturbation may be credited with certain cases of acquired homosexual feeling. Undoubtedly the instinct is occasionally evoked in some obscure way by the depraved habit of inordinate self-abuse. Yet the autobiographies of avowed Urnings do not corroborate the view that they were originally more addicted to onanism than normal males. Ulrichs has successfully combated the theory advanced by Tarnowsky, Prager, and Krafft-Ebing, if considered as a complete explanation of the problem.[25] On the other hand, common experience shows beyond all doubt, that young men between 16 and 20 give themselves up to daily self-abuse without weakening their appetite for women. They love boys and practice mutual self-abuse with persons of their own sex; yet they crave all the while for women. Of the many who live thus during the years of adolescence, some have undoubtedly as bad a family record as the worst of Krafft-Ebing's cases show. Finally, as regards the onanism which is a marked characteristic of some adult Urnings, this must be ascribed in most cases to the repression of their abnormal instincts. They adopt the habit, as Krafft-Ebing himself says, _faute de mieux_.[26] In justice to the theory I am criticising, it ought to be remarked that Krafft-Ebing does not contend that wherever hereditary taint and onanism concur, the result will be sexual inversion; but rather that wherever we have diagnosed an acquired form of sexual inversion, we shall discover hereditary taint and onanism. Considering the frequency of both hereditary taint and onanism in our civilisation, this is not risking much. Those factors are discoverable in a large percentage of male persons. What seems unwarranted by facts is the suggestion that inherited neuropathy is an indispensable condition and the fundamental cause of homosexual instincts. The evidence of ancient Greece, schools, prisons, and sotadic races, compels us to believe that normally healthy people are often born with these instincts or else acquire them by the way of custom. Again, his insinuation that onanism, regarded as the main exciting cause, is more frequent among young people of abnormal inclinations than among their normal brethren, will not bear the test of common observation and of facts communicated in the autobiographies of professed onanists and confessed Urnings.