Involuntary pollutions have been distinguished until now in another manner: they have been divided into _diurnal_ and _nocturnal_. These distinctions are founded only on accessory circumstances. What difference does it make, whether the pollutions occur by night or by day, provided they are similar in other respects? If, on the contrary, there are more essential differences, why not give to them the importance they demand? Farther: is not convulsive spermatorrhœa, like that which is not convulsive, seen both at night and day? These are the reasons why we have sought to distinguish these affections more logically, and which have led us to propose the new distinction just mentioned. Convulsive spermatorrhœa may occur in all individuals, and under the influence of a great many causes, without being necessarily a disease. After excessive continence, it may even prove a salutary crisis. This pollution has a pathological character, when it is repeated too often, or under unfavorable circumstances; and then it produces the same result as excesses in coition or masturbation, and generally occurs only in individuals already enfeebled by this kind of excess. Sleep is the most favorable state for an attack of spermatorrhœa; and from this circumstance it is called nocturnal pollution. The temperature of the bed, and lying on the back--circumstances which favor the warmth and excitement of the lower part of the spinal marrow--may also cause the convulsive excretion of the semen. But another cause of it is, that during the sleep of the external senses, the internal senses have control, and have more power, because the action of the others is completely suspended. Cabanis remarks this fact, in saying that the genital organs do not participate in the repose of the external senses, but seem to be more excitable when these are asleep. We consider, that what takes place then is analogous to what is observed in idiots, who, deaf, blind, and dead to all the feelings of relation, abandon themselves to every excess, to satisfy a sense, the excitement of which in them often amounts to constant satyriasis. If the sleep be very profound, pollution may take place without the consciousness of the patient, or, at any rate, without his remembrance of it. When he wakes, the loss of semen is then discovered only by its stain, and the state of fatigue, weakness, and malaise attending it. A lascivious dream, however, generally attends a pollution. These dreams are not, as is generally thought, the cause of the pollution: if they exist, it is because the venereal sense, which is excited, speaks for itself, even as hunger, thirst, or any internal sensation may do. These dreams have a peculiar character, which has been pointed out by many writers. The individual is rarely placed in voluptuous circumstances, where his imagination places him during his waking hours; but he is surrounded by females who are hideous and repelling, and whom he is as it were compelled to enjoy.