[131] This spectacle of the spider and the fly seems indeed to be specially apt to exert a sexual influence. I have heard of a precisely similar case in a man of intellectual distinction, and another in a lady who acknowledged to a feeling of "exquisite pleasure," on one occasion, at the mere sound of the death agony of a fly in a spider's web. [132] Quoted by Obici and Marchesini, _Le Amicizie di Collegio_, p. 245. [133] It may be noted that we have already several times encountered this increase of excitement produced by arrest of movement. The effect is produced whether the arrest is witnessed or is actually experienced. "A man can increase a woman's excitement," a lady writes, "by forbidding her to respond in any way to his caresses. It is impossible to remain quite passive for more than a few seconds, but, during these few, excitement is considerably augmented." In a similar way I have been told of a man of brilliant intellectual ability who very seldom has connection with a woman without getting her to compress with her hand the base of the urethral canal to such an extent as to impede the passage of the semen. On withdrawal of the hand copious emission occurs, but it is the shock of the arrest caused by the constriction which gives him supreme pleasure. He has practised this method for years without evil results. [134] Féré, "Le Sadisme aux Courses de Taureaux," _Revue de médecine_, August, 1900. [135] Féré, _L'Instinct sexuel_, p. 255. 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.