The present volume of Studies deals with some of the most essential problems of sexual psychology. The Analysis of the Sexual Impulse is fundamental. Unless we comprehend the exact process which is being worked out beneath the shifting and multifold phenomena presented to us we can never hope to grasp in their true relations any of the normal or abnormal manifestations of this instinct. I do not claim that the conception of the process here stated is novel or original. Indeed, even since I began to work it out some years ago, various investigators in these fields, especially in Germany, have deprived it of any novelty it might otherwise have possessed, while at the same time aiding me in reaching a more precise statement. This is to me a cause of satisfaction. On so fundamental a matter I should have been sorry to find myself tending to a peculiar and individual standpoint. It is a source of gratification to me that the positions I have reached are those toward which current intelligent and scientific opinions are tending. Any originality in my study of this problem can only lie in the bringing together of elements from somewhat diverse fields. I shall be content if it is found that I have attained a fairly balanced, general, and judicial statement of these main factors in the sexual instinct. In the study of Love and Pain I have discussed the sources of those aberrations which are commonly called, not altogether happily, "sadism" and "masochism." Here we are brought before the most extreme and perhaps the most widely known group of sexual perversions. I have considered them from the medico-legal standpoint, because that has already been done by other writers whose works are accessible. I have preferred to show how these aberrations may be explained; how they may be linked on to normal and fundamental aspects of the sexual impulse; and, indeed, in their elementary forms, may themselves be regarded as normal. In some degree they are present, in every case, at some point of sexual development; their threads are subtly woven in and out of the whole psychological process of sex. I have made no attempt to reduce their complexity to a simplicity that would be fallacious. I hope that my attempt to unravel these long and tangled threads will be found to make them fairly clear. In the third study, on The Sexual Impulse in Women, we approach a practical question of applied sexual psychology, and a question of the first importance. No doubt the sex impulse in men is of great moment from the social point of view. It is, however, fairly obvious and well understood. The impulse in women is not only of at least equal moment, but it is far more obscure. The natural difficulties of the subject have been increased by the assumption of most writers who have touched it-casually and hurriedly, for the most part-that the only differences to be sought in the sexual impulse in man and in woman are quantitative differences. I have pointed out that we may more profitably seek for qualitative differences, and have endeavored to indicate such of these differences as seem to be of significance.