ANALYSIS OF THE SEXUAL IMPULSE. Definition of Instinct—The Sexual Impulse a Factor of the Sexual Instinct—Theory of the Sexual Impulse as an Impulse of Evacuation—The Evidence in Support of this Theory Inadequate—The Sexual Impulse to Some Extent Independent of the Sexual Glands—The Sexual Impulse in Castrated Animals and Men—The Sexual Impulse in Castrated Women, After the Menopause, and in the Congenital Absence of the Sexual Glands—The Internal Secretions—Analogy between the Sexual Relationship and that of the Suckling Mother and her Child—The Theory of the Sexual Impulse as a Reproductive Impulse—This Theory Untenable—Moll's Definition—The Impulse of Detumescence—The Impulse of Contrectation—Modification of this Theory Proposed—Its Relation to Darwin's Sexual Selection—The Essential Element in Darwin's Conception—Summary of the History of the Doctrine of Sexual Selection. Its Psychological Aspect—Sexual Selection a Part of Natural Selection—The Fundamental Importance of Tumescence—Illustrated by the Phenomena of Courtship in Animals and in Man—The Object of Courtship is to Produce Sexual Tumescence—The Primitive Significance of Dancing in Animals and Man—Dancing is a Potent Agent for Producing Tumescence—The Element of Truth in the Comparison of the Sexual Impulse with an Evacuation, Especially of the Bladder—Both Essentially Involve Nervous Explosions—Their Intimate and Sometimes Vicarious Relationships—Analogy between Coitus and Epilepsy—Analogy of the Sexual Impulse to Hunger—Final Object of the Impulses of Tumescence and Detumescence. LOVE AND PAIN. I. The Chief Key to the Relationship between Love and Pain to be Found in Animal Courtship—Courtship a Source of Combativity and of Cruelty—Human Play in the Light of Animal Courtship—The Frequency of Crimes Against the Person in Adolescence—Marriage by Capture and its Psychological Basis—Man's Pleasure in Exerting Force and Woman's Pleasure in Experiencing it—Resemblance of Love to Pain even in Outward Expression—The Love-bite—In What Sense Pain May be Pleasurable—The Natural Contradiction in the Emotional Attitude of Women Toward Men—Relative Insensibility to Pain of the Organic Sexual Sphere in Women—The Significance of the Use of the Ampallang and Similar Appliances in Coitus—The Sexual Subjection of Women to Men in Part Explainable as the Necessary Condition for Sexual Pleasure. II. The Definition of Sadism—De Sade—Masochism to some Extent Normal—Sacher-Masoch—No Real Line of Demarcation between Sadism and Masochism—Algolagnia Includes Both Groups of Manifestations—The Love-bite as a Bridge from Normal Phenomena to Algolagnia—The Fascination of Blood—The Most Extreme Perversions are Linked on to Normal Phenomena. III. Flagellation as a Typical Illustration of Algolagnia—Causes of Connection between Sexual Emotion and Whipping—Physical Causes—Psychic Causes Probably More Important—The Varied Emotional Associations of Whipping—Its Wide Prevalence.