There is a further important difference, though intimately related to some of the differences already mentioned, between the sexual impulse in women and in men. In women it is at once larger and more diffused. As Sinibaldus long ago said, the sexual pleasure of men is intensive, of women extensive. In men the sexual impulse is, as it were, focused to a single point. This is necessarily so, for the whole of the essentially necessary part of the male in the process of human procreation is confined to the ejaculation of semen into the vagina. But in women, mainly owing to the fact that women are the child-bearers, in place of one primary sexual center and one primary erogenous region, there are at least three such sexual centers and erogenous regions: the clitoris (corresponding to the penis), the vaginal passage up to the womb, and the nipple. In both sexes there are other secondary and reflex centers, but there is good reason for believing that these are more numerous and more widespread in women than in men.[178] How numerous the secondary sexual centers in women may be is indicated by the case of a woman mentioned by Moraglia, who boasted that she knew fourteen different ways of masturbating herself. This great diffusion of the sexual impulse and emotions in women is as visible on the psychic as on the physical side. A woman can find sexual satisfaction in a great number of ways that do not include the sexual act proper, and in a great number of ways that apparently are not physical at all, simply because their physical basis is diffused or is to be found in one of the outlying sexual zones. It is, moreover, owing to the diffused character of the sexual emotions in women that it so often happens that emotion really having a sexual origin is not recognized as such even by the woman herself. It is possible that the great prevalence in women of the religious emotional state of "storm and stress," noted by Professor Starbuck,[179] is largely due to unemployed sexual impulse. In this and similar ways it happens that the magnitude of the sexual sphere in woman is unrealized by the careless observer. A number of converging facts tend to indicate that the sexual sphere is larger, and more potent in its influence on the organism, in women than in men. It would appear that among the males and females of lower animals the same difference may be found. It is stated that in birds there is a greater flow of blood to the ovaries than to the testes. In women the system generally is more affected by disturbances in the sexual sphere than in men. This appears to be the case as regards the eye. "The influence of the sexual system upon the eye in man," Power states, "is far less potent, and the connection, in consequence, far less easy to trace than in woman." (H. Power, "Relation of Ophthalmic Disease to the Sexual Organs," _Lancet_, November 26, 1887.)