[18] Thus it appears that sadism and masochism are not manifestations of “genital atavism” in the sense of Mantegazza and Lombroso, but are rather due to the gradual and pathological increase of physiological phenomena still manifest at the present day. CHAPTER IV PHYSICAL DIFFERENTIAL SEXUAL CHARACTERS “_We have here a_ primitive _inequality, whose primitiveness goes back to the opposition between content and form. From this primeval difference arise all the other secondary differences._”--ALFONS BILHARZ. CONTENTS OF CHAPTER IV Sexual differentiation as the primeval fact of human sexual life -- Waldeyer on the significance of sexual differentiation -- The biological law of Herbert Spencer -- Antagonism between reproductive and developmental tendencies -- Example of menstruation in illustration of this contrast -- The primitiveness of woman, and her greater proximity to nature -- Untenability of the notion of the “inferiority” of woman -- Views upon the nature of her physical development -- Increased differentiation of the sexes in consequence of civilization -- Comparison between medieval and modern pictures of women -- Obscuration of the sexual contrast in primitive times -- Examples -- Change of the voice in consequence of civilization -- Return to primitive conditions in certain phenomena of the emancipation of woman (the adoption of a masculine style of clothing, tobacco-smoking) -- Sexual indifference in the primitive history of mankind -- Connexion therewith of a primordial gynecocracy (according to Ratzel) -- Secondary sexual characters -- Principal difference between the masculine and the feminine body -- New researches on sexual differences -- Skeletal differences -- The specific sexual differences of the human pelvis -- Their dependence upon civilization and upon development of the brain -- Differences in body-size and body-weight -- In muscular and fatty development -- In the constitution of the blood -- Sexual differences in the larynx and the voice -- The skulls of men and women -- The weight of the brain -- No ground for the assumption of the inferiority of women -- Differences in brain-structure -- Researches of Rüdinger, Waldeyer, Broca, G. Retzius, etc. -- Recognition of the fact that the feminine type is somewhat infantile -- This type due to adaptation to the purposes of reproduction -- Masculine and feminine beauty -- Men and women different, but neither superior to the other. CHAPTER IV The difference between the sexes is the =original cause= of the human sexual life, the primeval preliminary of all human civilization. The existence of this difference can be proved, alike in physical and psychical relations, already in the fundamental phenomenon of human love, in which, because here the relations are simple and uncomplicated, it is most easily visible.