In the ordinary healthy organism, however, although the stimulants of strong emotion may be vaguely pleasurable, they do not have more than a general action on the sexual sphere, nor are they required for the due action of the sexual mechanism.  But in a slightly abnormal organism—­whether the anomaly is due to a congenital neuropathic condition, or to a possibly acquired neurasthenic condition, or merely to the physiological inadequacy of childhood or old age—­the balance of nervous energy is less favorable for the adequate play of the ordinary energies in courtship.  The sexual impulse is itself usually weaker, even when, as often happens, its irritability assumes the fallacious appearance of strength.  It has become unusually sensitive to unusual stimuli and also, it is possible,—­perhaps as a result of those conditions,—­more liable to atavistic manifestations.  An organism in this state becomes peculiarly apt to seize on the automatic sources of energy generated by emotion.  The parched sexual instinct greedily drinks up and absorbs the force it obtains by applying abnormal stimuli to its emotional apparatus.  It becomes largely, if not solely, dependent on the energy thus secured.  The abnormal organism in this respect may become as dependent on anger or fear, and for the same reason, as in other respects it may become dependent on alcohol.

We see the process very well illustrated by the occasional action of the emotion of anger.  In animals the connection between love and anger is so close that even normally, as Groos points out, in some birds the sight of an enemy may call out the gestures of courtship.[139] As Krafft-Ebing remarks, both love and anger “seek their object, try to possess themselves of it, and naturally exhaust themselves in a physical effect on it; both throw the psychomotor sphere into the most intense excitement, and by means of this excitement reach their normal expression."[140] Fere has well remarked that the impatience of desire may itself be regarded as a true state of anger, and Stanley Hall, in his admirable study of anger, notes that “erethism of the breasts or sexual parts” was among the physical manifestations of anger occurring in some of his cases, and in one case a seminal emission accompanied every violent outburst.[141] Thus it is that anger may be used to reinforce a weak sexual impulse, and cases have been recorded in which coitus could only be performed when the man had succeeded in working himself up into an artificial state of anger.[142] On the other hand, Fere has recorded a case in which the sexual excitement accompanying delayed orgasm was always transformed into anger, though without any true sadistic manifestations.[143]