This failure to recognise the equivalent value of internal with external structure has led to such crude fallacy as a comparison of the penis with such a vestige as the clitoris, whilst failing to recognise that vast amount of erectile tissue, mostly internal, in the female, which is the direct seat of special sexual spasm; such superficial observation also fails to realize that sexual attraction is not limited by any isolated physical act. The true nature of semen remained unknown during ages of physiological ignorance. It was regarded as the one essential element in reproduction, planted for growth in the uterus, where it was simply nourished by the female. The moving particles contained in it were regarded as animalculæ, and fanciful theories as to these particles forming the brain and nervous system, etc., of the embryo were entertained. But all these theories have been swept away by modern investigation. It is now proved that when the substances of spermatozoa and ova mingle a new action is set up, and an entirely new substance created. Life, in the true sense of separate individuality, only begins with the mingling of the male and female elements, the commencement of a new existence then taking place when the living ovum fixes itself in the uterus, and remains there for full growth and final birth. The substance of spermatozoa and the substance of ova possess no sanctity of life apart from their union. They are both produced in lavish abundance, and thrown off from the body in the same way as other unused secretions are thrown off. At the periods of menstruation unused ova are discharged. In a similar manner unused semen is thrown off from time to time, in an entirely healthy and beneficent way, by spontaneous natural action. As ovulation in the female and sperm-formation in the male are equivalent productions, so menstruation in the female and natural sperm-emission in the male are analogous and beneficial functions. It is in the arrangement of these two functions in man that the physical sexual superiority of mankind to the brute creation lies. The reason of the two distinctive laws which govern human sex is evident. Thus: 1st. Continuity of action. Procreation in man is not limited to any special season.[1] Men and women can be governed by reason as to the time and circumstances when they select one another and commence the important work of founding a family. The physical organs are maintained in fit condition for reproduction by these functions of ovulation and spermation, as servants ready to obey at any time the superior intelligence of the master Will.