congenital and acquired homosexuality has ceased to possess significance.  When we have recognized that there is a tendency for homosexuality to arise in persons of usually normal tendency who are placed under conditions (as on board ship or in prison) where the exercise of normal sexuality is impossible, there is little further classification to be achieved along this line.[129] We have gone as far as is necessary by admitting a general undefined homosexuality,—­a relationship of unspecified nature to persons of the same sex,—­in addition to the more specific sexual inversion.[130]

It may now be said to be recognized by all authorities, even by Freud who emphasizes a special psychological mechanism by which homosexuality may become established, that a congenital predisposition as well as an acquired tendency is necessary to constitute true inversion, apparent exceptions being too few to carry much weight.  Krafft-Ebing, Naecke, Iwan Bloch, who at one time believed in the possibility of acquired inversion, all finally abandoned that view, and even Schrenck-Notzing, a vigorous champion of the doctrine of acquired inversion twenty years ago, admits the necessity of a favoring predisposition, an admission which renders the distinction between innate and acquired an unimportant, if not a merely verbal, distinction.[131] Supposing, indeed, that we are prepared to admit that true inversion may be purely acquired the decision in any particular case must be extremely difficult, and I have found very few cases which, even with imperfect knowledge, could fairly so be termed.

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 Naecke 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]