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. IV. The Impulse to Strangle the Object of Sexual Desire--The Wish to be Strangled. Respiratory Disturbance the Essential Element in this Group of Phenomena--The Part Played by Respiratory Excitement in the Process of Courtship--Swinging and Suspension--The Attraction Exerted by the Idea of being Chained and Fettered. V. Pain, and not Cruelty, the Essential Element in Sadism and Masochism--Pain Felt as Pleasure--Does the Sadist Identify Himself with the Feelings of his Victim?--The Sadist Often a Masochist in Disguise--The Spectacle of Pain or Struggle as a Sexual Stimulant. VI. Why is Pain a Sexual Stimulant?--It is the Most Effective Method of Arousing Emotion--Anger and Fear the Most Powerful Emotions--Their Biological Significance in Courtship--Their General and Special Effects in Stimulating the Organism--Grief as a Sexual Stimulant--The Physiological Mechanism of Fatigue Renders Pain Pleasurable. VII. Summary of Results Reached--The Joy of Emotional Expansion--The Satisfaction of the Craving for Power--The Influence of Neurasthenic and Neuropathic Conditions--The Problem of Pain in Love Largely Constitutes a Special Case of Erotic Symbolism. THE SEXUAL IMPULSE IN WOMEN. Introduction. I.