The sexual interest of children generally turns first to the mystery of birth--the same problem that is the basis of the questions asked by the sphinx of Thebes. This curiosity is for the most part aroused by the selfish fear of the arrival of a new child. The answer which the nursery has ready for the child, that the stork brings children, is doubted far more frequently than we imagine, even by very young children. The feeling that he has been cheated out of the truth by grown-ups, contributes greatly to the child's sense of solitude and to his independent development. But the child is not capable of solving this problem unaided. His undeveloped sexual constitution restricts his ability to understand. At first he assumes that children are produced by a special substance in one's food and does not know that only women can bear children. Later he learns of this limitation and relinquishes the derivation of children from food--a supposition retained in the fairy-tale. The growing child soon notices that the father plays some part in reproduction, but what it is he cannot guess. If, by chance, he is witness of a sexual act, he sees in it an attempt to subjugate, a scuffle, the sadistic miscomprehension of coitus; he does not however relate this act immediately to the evolution of the child. When he discovers traces of blood on the bedsheets or on the clothing of his mother, he considers them the proof of an injury inflicted by the father. During the latter part of childhood, he imagines that the sexual organ of the man plays an important part in the evolution of children, but can ascribe only the function of urination to that part of his body.
From the very outset children unite in believing that the birth of the child takes place through the anus; that the child therefore appears as a ball of faeces. After anal interests have been proven valueless, he abandons this theory and assumes that the navel opens or that the region between the two breasts is the birthplace of the child. In this way the curious child approaches the knowledge of sexual facts, which, clouded by his ignorance, he often fails to see. In the years prior to puberty he generally receives an incomplete, disparaging explanation which often causes traumatic consequences.