The sexual interest of children is primarily directed to the problem of birth—the same problem that lies behind the riddle of the Theban Sphinx. This curiosity is for the most part aroused by egoistic dread of the arrival of another child. The answer which the nursery has ready for the child, that the stork brings the babies, meets with incredulity even in little children much more often than we imagine. The feeling of having been deceived by grown-up people, and put off with lies, contributes greatly to a sense of isolation and to the development of independence. But the child is not able to solve this problem on his own account. His undeveloped sexual constitution sets definite limits to his capacity to understand it. He first supposes that children are made by mixing some special thing with the food taken; nor does he know that only women can have children. Later, he learns of this limitation and gives up the idea of children being made by food, though it is retained in fairy tales. A little later he soon sees that the father must have something to do with making babies, but he cannot discover what it is. If by chance he is witness of the sexual act he conceives it as an attempt to overpower the woman, as a combat, the sadistic misconception of coitus; at first, however, he does not connect this act with the creation of children; if he discovers blood on the mother’s bed or underlinen he takes it as evidence of injury inflicted by the father. In still later years of childhood he probably guesses that the male organ of the man plays an essential part in the procreation of children, but cannot ascribe to this part of the body any function but that of urination. Children are all united from the outset in the belief that the birth of a child takes place by the bowel; that is to say, that the baby is produced like a piece of fæces. Not until all interest has been weaned from the anal region is this theory abandoned and replaced by the supposition that the navel opens, or that the area between the two nipples is the birthplace of the child. In some such manner as this the enquiring child approaches some knowledge of the facts of sex, unless, misled by his ignorance, he overlooks them until he receives an imperfect and discrediting account of them, usually in the period before puberty, which not infrequently affects him traumatically.