Nor are such relationships found to be confined to these two centers; in a lesser degree the more remote explosive centers are also affected; all motor influences may spread to related muscles; the convulsion of laughter, for instance, seems to be often in relation with the sexual center, and Groos has suggested that the laughter which, especially in the sexually minded, often follows allusions to the genital sphere is merely an effort to dispel nascent sexual excitement by liberating an explosion of nervous energy in another direction.[57] Nervous discharges tend to spread, or to act vicariously, because the motor centers are more or less connected.[58] Of all the physiological motor explosions, the sexual orgasm, or detumescence, is the most massive, powerful, and overwhelming. So volcanic is it that to the ancient Greek philosophers it seemed to be a minor kind of epilepsy. The relief of detumescence is not merely the relief of an evacuation; it is the discharge, by the most powerful apparatus for nervous explosion in the body, of the energy accumulated and stored up in the slow process of tumescence, and that discharge reverberates through all the nervous centers in the organism. "The sophist of Abdera said that coitus is a slight fit of epilepsy, judging it to be an incurable disease." (Clement of Alexandria, _Pædagogus_, bk. ii, chapter x.) And Coelius Aurelianus, one of the chief physicians of antiquity, said that "coitus is a brief epilepsy." Féré has pointed out that both these forms of nervous storm are sometimes accompanied by similar phenomena, by subjective sensations of sight or smell, for example; and that the two kinds of discharge may even be combined. (Féré, _Les Epileptiques_, pp. 283-84; also "Exces Vénériens et Epilepsie," _Comptes-rendus de la Société de Biologie_, April 3, 1897, and the same author's _Instinct Sexuel_, pp. 209, 221, and his "Priapisme Epileptique," _La Médecine Moderne_, February 4, 1899.) The epileptic convulsion in some cases involves the sexual mechanism, and it is noteworthy that epilepsy tends to appear at puberty. In modern times even so great a physician as Boerhaave said that coitus is a "true epilepsy," and more recently Roubaud, Hammond, and Kowalevsky have emphasized the resemblance between coitus and epilepsy, though without identifying the two states. Some authorities have considered that coitus is a cause of epilepsy, but this is denied by Christian, Strümpell, and Löwenfeld. (Löwenfeld, _Sexualleben und Nervenleiden_, 1899, p. 68.) Féré has recorded the case of a youth in whom the adoption of the practice of masturbation, several times a day, was followed by epileptic attacks which ceased when masturbation was abandoned. (Féré, _Comptes-rendus de la Socitété de Biologie_, April 3, 1897.)