The reader, however, who has followed the discussion to this point will be prepared to take the next and final step in our discussion and to reach a more definite conclusion.  The question naturally arises:  By what process does pain or its mental representation thus act as a sexual stimulant?  The answer has over and over again been suggested by the facts brought forward in this study.  Pain acts as a sexual stimulant because it is the most powerful of all methods for arousing emotion.

The two emotions most intimately associated with pain are anger and fear.  The more masculine and sthenic emotion of anger, the more passive and asthenic emotion of fear, are the fundamental animal emotions through which, on the psychic side, the process of natural selection largely works.  Every animal in some degree owes its survival to the emotional reaction of anger against weaker rivals, to the emotional reaction of fear against stronger rivals.  To this cause we owe it that these two emotions are so powerfully and deeply rooted in the whole zooelogical series to which we belong.  But anger and fear are not less fundamental in the sexual life.  Courtship on the male’s part is largely a display of combativity, and even the very gestures by which the male seeks to appeal to the female are often those gestures of angry hostility by which he seeks to intimidate enemies.  On the female’s part courtship is a skillful manipulation of her own fears, and, as we have seen elsewhere, when studying the phenomena of modesty, that fundamental attitude of the female in courtship is nothing but an agglomeration of fears.

The biological significance of the emotions is now well recognized.  “In general,” remarks one of the shrewdest writers on animal psychology, “we may say that emotional states are, under natural conditions, closely associated with behavior of biological value—­with tendencies that are beneficial in self-preservation and race preservation—­with actions that promote survival, and especially with the behavior which clusters round the pairing and parental instincts.  The value of the emotions in animals is that they are an indirect means of furthering survival.” (Lloyd Morgan, Animal Behavior, p. 293.) Emotional aptitudes persist not only by virtue of the fact that they are still beneficial, but because they once were; that is to say, they may exist as survivals.  In this connection I may quote from a suggestive paper on “Teasing and Bullying,” by F.L.  Burk; at the conclusion of this study, which is founded on a large body of data concerning American children, the author asks:  “Accepting for the moment the theories of Spencer and Ribot upon the transmission of rudimentary instincts, is it possible that the movements which comprise the chief elements of bullying, teasing, and the egotistic impulses in general of the classes cited—­pursuing, throwing down, punching, striking, throwing missiles, etc.—­are, from the standpoint of consciousness, broken neurological