owing to their strictly scientific character they are not so noisily obtruded on the public notice as are certain other widely advertised and reputedly scientific works. In his various books, and above all in his six volumes entitled _Studies in the Psychology of Sex_ (F. A. Davies Company, Philadelphia, Pa.), as a part of his general contributions to our knowledge of the sexual life, Havelock Ellis records numerous observations relating to the years of childhood; especially valuable in this connexion are the biographies given in the third volume of the above-mentioned _Studies_. A valuable source of data for our field of inquiry exists in the form of unpublished diaries, autobiographies, and albums, which are not accessible to the general public. I have myself had the opportunity of studying a number of records of this nature, and have formed the opinion that a quantity of invaluable material lies hidden in these recesses. I may add that the records I have been able to use have not only related to living persons; in addition, I have been able to study a number of albums and diaries dating from an earlier day. These have remained unpublished, in part because they appeared to be of interest only to the families of the writers, and in part because many of them were in intention purely private memoranda, a written record for the sole use of the writer. Speaking generally, however, this province of research has received but little scientific attention; and of comprehensive studies, intended to throw light on every aspect of the sexual life of the child, not a single one is known to me. Chapter II THE SEXUAL ORGANS--THE SEXUAL IMPULSE A proper understanding of physiological functions is based upon anatomical knowledge of the organs concerned. For our purpose, therefore, a knowledge of the sexual organs of the child is essential. The proper course, in this instance, appears to be to start with an account of the adult organs, and then to describe the distinctive characteristics of the same organs in the child. Let us, then, begin with the organs of the adult man.