Ellis' 1933 book, Psychology of Sex, is one of the many manifestations of his interest in human sexuality. In this book, he goes into vivid detail of how children can experience sexuality differently in terms of time and intensity. He mentions that it was previously believed that, in childhood, humans had no sex impulse at all. "If it is possible to maintain that the sex impulse has no normal existence in early life, then every manifestation of it at that period must be 'perverse,'" he adds. He continues by stating that, even in the early development and lower function levels of the genitalia, there is a wide range of variation in terms of sexual stimulation. He claims that the ability of some infants producing genital reactions, seen as "reflex signs of irritation" are typically not vividly remembered. Since the details of these manifestations are not remembered, there is no possible way to determine them as pleasurable. However, Ellis claims that many people of both sexes can recall having agreeable sensations with the genitalia as a child. "They are not (as is sometimes imagined) repressed." They are, however, not usually mentioned to adults. Ellis argues that they typically stand out and are remembered for the sole contrast of the intense encounter to any other ordinary experience.

THE EVOLUTION OF MODESTY
I.
The Definition of Modesty?The Significance of Modesty?Difficulties in the Way of Its Analysis?The Varying Phenomena of Modesty Among Different Peoples and in Different Ages.

II.
Modesty an Agglomeration of Fears?Children in Relation to Modesty?Modesty in Animals?The Attitude of the Medicean Venus?The Sexual Factor of Modesty Based on Sexual periodicity and on the Primitive Phenomena of Courtship?The Necessity of Seclusion in Primitive Sexual Intercourse?The Meaning of Coquetry?The Sexual Charm of Modesty?Modesty as an Expression of Feminine Erotic Impulse?The Fear of Causing Disgust as a Factor of Modesty?The Modesty of Savages in Regard to Eating in the Presence of Others?The Sacro-Pubic Region as a Focus of Disgust?The Idea of Ceremonial Uncleanliness?The Custom of Veiling the Face?Ornaments and Clothing?Modesty Becomes Concentrated in the Garment?The Economic Factor in Modesty?The Contribution of Civilization to Modesty?The Elaboration of Social Ritual.

III.
The Blush the Sanction of Modesty?The Phenomena of Blushing?Influences Which Modify the Aptitude to Blush?Darkness, Concealment of the Face, Etc.

IV.
Summary of the Factors of Modesty?The Future of Modesty?Modesty an Essential Element of Love.

THE PHENOMENA OF SEXUAL PERIODICITY
I.
The Various Physiological and Psychological Rhythms?Menstruation?The Alleged Influence of the Moon?Frequent Suppression of Menstruation among Primitive Races?Mittelschmerz?Possible Tendency to a Future Intermenstrual Cycle?Menstruation among Animals?Menstruating Monkeys and Apes?What is Menstruation?Its Primary Cause Still Obscure?The Relation of Menstruation to Ovulation?The Occasional Absence of Menstruation in Health?The Relation of Menstruation to "Heat"?The Prohibition of Intercourse during Menstruation?The Predominance of Sexual Excitement at and around the Menstrual Period?Its Absence during the Period Frequently Apparent only.

II.
The Question of a Monthly Sexual Cycle in Men?The Earliest Suggestions of a General Physiological Cycle in Men?Periodicity in Disease?Insanity, Heart Disease, etc.?The Alleged Twenty-three Days' Cycle?The Physiological Periodicity of Seminal Emissions during Sleep?Original Observations?Fortnightly and Weekly Rhythms.

III.
The Annual Sexual Rhythm?In Animals?In Man?Tendency of the Sexual Impulse to become Heightened in Spring and Autumn?The Prevalence of Seasonal Erotic Festivals?The Feast of Fools?The Easter and Midsummer Bonfires?The Seasonal Variations in Birthrate?The Causes of those Variations?The Typical Conception-rate Curve for Europe?The Seasonal Periodicity of Seminal Emissions During Sleep?Original Observations?Spring and Autumn the Chief Periods of Involuntary Sexual Excitement?The Seasonal Periodicity of Rapes?Of Outbreaks among Prisoners?The Seasonal Curves of Insanity and Suicide?The Growth of Children According to Season?The Annual Curve of Bread-consumption in Prisons?Seasonal Periodicity of Scarlet Fever?The Underlying Causes of these Seasonal Phenomena.

AUTO-EROTISM: A STUDY OF THE SPONTANEOUS MANIFESTATIONS OF THE SEXUAL IMPULSE

I.
Definition of Auto-erotism?Masturbation only Covers a Small Portion of the Auto-erotic Field?The Importance of this Study, especially To-day?Auto-erotic Phenomena in Animals?Among Savage and Barbaric Races?The Japanese rin-no-tama and other Special Instruments for Obtaining Auto-erotic Gratification?Abuse of the Ordinary Implements and Objects of Daily Life?The Frequency of Hair-pin in the Bladder?The Influence of Horse-exercise and Railway Traveling?The Sewing-machine and the Bicycle?Spontaneous Passive Sexual Excitement?Delectatio Morosa?Day-dreaming?Pollutio?Sexual Excitement During Sleep?Erotic Dreams?The Analogy of Nocturnal Enuresis?Differences in the Erotic Dreams of Men and Women?The Auto-erotic Phenomena of Sleep in the Hysterical?Their Frequently Painful Character.

II.
Hysteria and the Question of Its Relation to the Sexual Emotions?The Early Greek Theories of its Nature and Causation?The Gradual Rise of Modern Views?Charcot?The Revolt Against Charcot's Too Absolute Conclusions?Fallacies Involved?Charcot's Attitude the Outcome of his Personal Temperament?Breuer and Freud?Their Views Supplement and Complete Charcot's?At the Same Time they Furnish a Justification for the Earlier Doctrine of Hysteria?But They Must Not be Regarded as Final?The Diffused Hysteroid Condition in Normal Persons?The Physiological Basis of Hysteria?True Pathological Hysteria is Linked on to almost Normal States, especially to Sex-hunger.

III.
The Prevalence of Masturbation?Its Occurrence in Infancy and Childhood?Is it More Frequent in Males or Females??After Adolescence Apparently more Frequent in Women?Reasons for the Sexual Distribution of Masturbation?The Alleged Evils of Masturbation?Historical Sketch of the Views Held on This Point?The Symptoms and Results of Masturbation?Its Alleged Influence in Causing Eye Disorders?Its Relation to Insanity and Nervous Disorders?The Evil Effects of Masturbation Usually Occur on the Basis of a Congenitally Morbid Nervous System?Neurasthenia Probably the Commonest Accompaniment of Excessive Masturbation?Precocious Masturbation Tends to Produce Aversion to Coitus?Psychic Results of Habitual Masturbation?Masturbation in Men of Genius?Masturbation as a Nervous Sedative?Typical Cases?The Greek Attitude toward Masturbation?Attitude of the Catholic Theologians?The Mohammedan Attitude?The Modern Scientific Attitude?In What Sense is Masturbation Normal??The Immense Part in Life Played by Transmuted Auto-erotic Phenomena.

APPENDIX A.
The Influence of Menstruation on the Position of Women.

APPENDIX B.
Sexual Periodicity in Men.

APPENDIX C.
The Auto-erotic Factor in Religion.