"The emotion of love between the sexes has as yet received no thorough scientific treatment. No writer so far as I can find has treated it from a genetic standpoint. The literature upon the subject is therefore meager. In his recent treatise upon "The Psychology of the Emotions, " Ribot remarks: "The sex-instinct, the last in chronological order with man and the higher animals, gives rise to the emotion of love with its numerous individual varieties. Most psychologists have been very sparing of details where it is concerned, and one might mention certain voluminous treatises which contain no mention of it. Is this through exaggerated delicacy? Or is it because the authors think that their place has been usurped by the novelists who have so obstinately confined themselves to the study of this passion? But the novelist's mode of analysis is different from the psychological mode, and does not exclude it. ""