Even the cases (to which Schopenhauer long since referred) in which inversion is only established late in life, are no longer regarded as constituting a difficulty in accepting the doctrine of the congenital nature of inversion; in such cases the inversion is merely retarded. The conception of retarded inversion,--that is to say a latent congenital inversion becoming manifest at a late period in life,--was first brought forward by Thoinot in 1898 in his _Attentats aux Moeurs_, in order to supersede the unsatisfactory conception, as he considered it to be, of acquired inversion. Thoinot regarded retarded inversion as relatively rare and of no great importance but more accessible to therapeutic measures. Three years later, Krafft-Ebing, toward the close of his life, adopted the same conception; the cases to which he applied it were all, he considered, of bisexual disposition and usually, also, marked by sexual hyperesthesia. This way of looking at the matter was speedily championed by Näcke and may now be said to be widely accepted.[132] Moll, earlier than Thoinot, had pointed out that it is difficult to believe that homosexuality in late life can ever be produced without at least some inborn weakness of the heterosexual impulse, and that we must not deny the possibility of heredity even when homosexuality appears at the age of 50 or 60.[133] Moll believes it is very doubtful whether heterosexual satiety alone can ever suffice to produce homosexuality. Näcke was careful to set aside the cases, to which much significance was once attached, in which old men with failing sexual powers, or younger men exhausted by heterosexual debauchery, are attracted to boys. In such cases, which include the majority of those appearing late, Näcke regarded the inversion as merely spurious, the _faute de mieux_ of persons no longer apt for normal sexual activity.