I do not believe that an undifferentiated stage occurs in every one without exception. On the other hand, I have absolutely no doubt that it occurs very frequently indeed--far more frequently than is commonly believed--and that it occurs in persons whose subsequent sexual development is perfectly normal. Moreover, during the undifferentiated stage, in addition to heterosexual and homosexual inclinations, perverse sentiments may make their appearance. Masochistic, sadistic, fetichistic excitations of all kinds are met with, and sexual inclination towards animals is by no means rare. As regards the last named, the inclination is directed especially towards the animals with which the child is most intimately associated, as, for instance, a dog, a cat, a bird, a horse, and the like. Again, during the period of undifferentiated sexual impulse all kinds of disordered ideas may become associated with that impulse; for instance, an impulse may arise to touch the saliva, or some other excretory product, of the beloved being, human or animal, as the case may be, and even to take such a product into the mouth. Many persons completely forget all these manifestations of the undifferentiated sexual impulse which have formed part of their own early experiences. The causes of such oblivion have been discussed in the first chapter (p. 5). Yet another reason may be mentioned for regarding a knowledge of the undifferentiated stage of the sexual impulse as of great importance. In works on the pathology of the sexual impulse we are frequently assured that in this or that specific instance the perversion was inborn, because perverse sensations have existed since the days of childhood. But the existence of the undifferentiated stage teaches us that we are not justified in inferring, from the mere fact of the primary occurrence of a "perverse" mode of sexual sensibility, that this perversion is congenital; for the primary direction of the contrectation impulse during the undifferentiated stage often depends to a considerably greater extent upon chance than upon an inherited predisposition.