Kiernan appears to have been the first to suggest the bearing of these facts on sadism, which he would regard as the abnormal human form of phenomena which may be found at the very beginning of animal life, as, indeed, the survival or atavistic reappearance of a primitive sexual cannibalism. See his “Psychological Aspects of the Sexual Appetite,” Alienist and Neurologist, April, 1891, and “Responsibility in Sexual Perversion,” Chicago Medical Recorder, March, 1892. Penta has also independently developed the conception of the biological basis of sadism and other sexual perversions (I Pervertimenti Sessuali, 1893). It must be added that, as Remy de Gourmont points out (Promenades Philosophiques, 2d series, p. 273), this sexual cannibalism exerted by the female may have, primarily, no erotic significance: “She eats him because she is hungry and because when exhausted he is an easy prey.”
 In the chapter entitled “Le Vol Nuptial” of his charming book on the life of bees Maeterlinck has given an incomparable picture of the tragic courtship of these insects.
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.
The whole problem of love and pain, in its complementary sadistic and masochistic aspects, is presented to us in connection with the pleasure sometimes experienced in whipping, or in being whipped, or in witnessing or thinking about scenes of whipping. The association of sexual emotion with bloodshed is so extreme a perversion, it so swiftly sinks to phases that are obviously cruel, repulsive, and monstrous in an extreme degree, that it is necessarily rare, and those who are afflicted by it are often more or less imbecile. With whipping it is otherwise. Whipping has always been a recognized religious penance; it is still regarded as a beneficial and harmless method of chastisement; there is nothing necessarily cruel, repulsive, or monstrous in the idea or the reality of whipping, and it is perfectly easy and natural for an interest in the subject to arise in an innocent and even normal child, and thus to furnish a germ around which, temporarily at all events, sexual ideas may crystallize. For these reasons the connection between love and pain may be more clearly brought out in connection with whipping than with blood.
There is, by no means, any necessary connection between flagellation and the sexual emotions. If there were, this form of penance would not have been so long approved or at all events tolerated by the Church.