This affection may arise from different causes. It is owing most frequently to venereal excesses; and, as but little is known in regard to it, we shall enlarge on the subject. This pollution for a long time was confounded with all the discharges from the urethra, which were blended under the term gonorrhœa. A contrary opinion was then adopted, and the existence of the disease was denied _in toto_. The remarks of several authors, and particularly of Wichmann, Sante Marie, and Lallemand, place its existence, however, beyond a doubt. The first ideas on this kind of spermatorrhœa may be referred to the earliest periods of medicine. It was known to Hippocrates, who has mentioned (_De Morbis_, lib. ii., sect. 5) one of the principal symptoms, the loss of semen, during the emission of urine, and of feces, when describing the tabes dorsalis which affects libertines and those lately married. Celsus, also, (_De Medicina_, lib. iv., ch. 28,) has admitted that there may be loss of semen, without pleasure, without voluptuous dreams, and which may be followed by a fatal consumption. After this, we find no mention of the disease for a long period. Tauvry says positively, (_Naw. Anat. raisonnée_, 1693, p. 164,) that men who abuse themselves are liable to have emissions of semen on the slightest compression of the seminal vesicles, when they pass urine or feces. Morgagni admits that the semen may escape without any pleasurable sensation, as happens from the effect of an injection which is too warm, and from the excretion of hardened feces; but he adds, that the fluid discharged may come in some from the prostate gland, in others, from the seminal vesicles. There is much uncertainty on this point of science among authors, many of whom have considered as spermatic most of the discharges from the urethra. The dissertation of Wichmann, however, on the subject of diurnal pollution, is valuable. This dissertation was printed in 1782, at Gœttingen. In it, Wichmann states, first, the characters which distinguish diurnal from nocturnal pollution. The first occurs when the patient is awake, and without his experiencing erection or desire. He is unconscious of it; and this circumstance, with the absence of any swelling of the corpora cavernosa, and of all venereal ardor, serves to distinguish this pollution from the flow of the fluid of the prostate gland, or from a loss of semen, which takes place in some persons when they are excited by desire. To these characters, Wichmann adds another, drawn from the mode in which the excretion of semen takes place. In diurnal pollution, (says he,) men do not lose their semen constantly by a continual excretion of this fluid, like females subject to leucorrhea; but they ejaculate, at a single time: and this circumstance has rendered the term pollution applicable to this disease. He does not consider, as a diurnal pollution, the gonorrhœa in which the semen is continually escaping drop by drop. He, however, doubts the existence of this last affection, and remarks that authors are very much confused on the subject. Nor would a pollution which was involuntary, and during the hours of waking, be considered as a diurnal pollution, if the evacuation of semen had been caused by any aphrodisiac substance. And on this topic, he relates the case of a man, who, having been addicted to onanism in his youth, was affected with involuntary pollutions if a blister was applied to him, if he perceived the odor of cantharides, or even spoke of them.