III.

Summary of Conclusions.

APPENDIX A.

The Sexual Instinct in Savages.

APPENDIX B.

The Development of the Sexual Instinct.

INDEX OF AUTHORS.

INDEX OF SUBJECTS.

ANALYSIS OF THE SEXUAL IMPULSE.

Definition of Instinct—­The Sexual Impulse a Factor of the Sexual Instinct—­Theory of the Sexual Impulse as an Impulse of Evacuation—­The Evidence in Support of this Theory Inadequate—­The Sexual Impulse to Some Extent Independent of the Sexual Glands—­The Sexual Impulse in Castrated Animals and Men—­The Sexual Impulse in Castrated Women, after the Menopause, and in the Congenital Absence of the Sexual Glands—­The Internal Secretions—­Analogy between the Sexual Relationship and that of the Suckling Mother and her Child—­The Theory of the Sexual Impulse as a Reproductive Impulse—­This Theory Untenable—­Moll’s Definition—­The Impulse of Detumescence—­The Impulse of Contrectation—­Modification of this Theory Proposed—­Its Relation to Darwin’s Sexual Selection—­The Essential Element in Darwin’s Conception—­Summary of the History of the Doctrine of Sexual Selection—­Its Psychological Aspect—­Sexual Selection a Part of Natural Selection—­The Fundamental Importance of Tumescence—­Illustrated by the Phenomena of Courtship in Animals and in Man—­The Object of Courtship is to Produce Sexual Tumescence—­The Primitive Significance of Dancing in Animals and Man—­Dancing is a Potent Agent for Producing Tumescence—­The Element of Truth in the Comparison of the Sexual Impulse with an Evacuation, Especially of the Bladder—­Both Essentially Involve Nervous Explosions—­Their Intimate and Sometimes Vicarious Relationships—­Analogy between Coitus and Epilepsy—­Analogy of the Sexual Impulse to Hunger—­Final Object of the Impulses of Tumescence and Detumescence.

The term “sexual instinct” may be said to cover the whole of the neuropsychic phenomena of reproduction which man shares with the lower animals.  It is true that much discussion has taken place concerning the proper use of the term “instinct,” and some definitions of instinctive action would appear to exclude the essential mechanism of the process whereby sexual reproduction is assured.  Such definitions scarcely seem legitimate, and are certainly unfortunate.  Herbert Spencer’s definition of instinct as “compound reflex action” is sufficiently clear and definite for ordinary use.