I refer the reader to textbooks in anatomy and embryology, and to the specialists on sex like Krafft-Ebbing, Havelock Ellis and Ploss for details as to the differences between man and woman. There are first the essential organs of generation, differing in the two sexes, the ovary furnishing the egg, the testes furnishing the seed or sperm; then the organs of sexual contact; the secondary sex characteristics, such as stature, distribution of hair, deposits of fat, shape of body and especially of the pelvis, the voice, smoothness of skin, muscular development, etc. There is an orderly evolution in the development of sex characters which starts with earliest embryo life and goes on regularly until puberty, when there is an extraordinary development of latent characters and peculiarities. After puberty maturity is reached by easy stages, and then comes involution or the recession of sex characters. This is reached in woman rather suddenly and in man more gradually. The completely differentiated man differs from his completely differentiated mate in the texture of his hair, skin, nails; in the width and mobility of pupils, in the color of his sclera, etc., as well as in the more essential sex organs. Indeed there are very essential bodily differences that are obviously important though not well understood. One is that the bodily temperature of man is slightly higher than that of woman, and that he has five million red blood corpuscles to every cubic millimeter of his blood, while she has four and a half million; that his brain weighs considerably more but is not heavier proportionately; that her bodily proportions resemble those of the child-form[1] more than do his, which some interpret as a point of superiority for her, while others interpret it as a sign of inferiority. On the whole, the authorities consider that man is made for the discharge of energy at a high rate for a short time, he is the katabolic element, while woman stores up energy for her children and represents the anabolic element of the race. [1] See Havelock Ellis. As a corollary to the above, it is necessary to know that each human being (and also each higher animal) starts out with the potential sex organs of both sexes, and that each individual becomes sexually differentiated at about the eleventh week of intra-uterine life. Moreover every male has female organs, and every female has male organs, though in the normal conditions these are mere vestiges and play no part in the sex life of the person. Yet this indicates that the separation of male and female is not absolute, and logically and actually a male may have female characters, physically and mentally, and vice versa a female may resemble the male in structure and character.