Inquiry among a large number of normal healthy men convinces the author that it is not at all unusual for these emissions to occur as infrequently as once in two months in normal healthy men. On the other hand, it is not unusual for them to occur as frequently as once in ten days or even once a week and still be within the physiological limit. However, when the emission occurs as frequently as once per week, it should be looked upon as abnormal if it is followed by depression, headache or lassitude. Cases are not unusual in which the nocturnal emission is experienced as often as three times in a week after which there will be a period of two to four weeks without an emission, followed again by very frequent emissions, and a free period. This phenomenon is an individual peculiarity, and is not to be looked upon as abnormal.
Cases of too frequent nocturnal emissions accompanied by languor and headache are usually caused by irritability or lack of tonicity of the sexual apparatus, particularly of the seminal vesicles and the ducts. This irritability and loss of tone is not infrequently caused by masturbation, though it may also be caused by excessive sexual intercourse, making itself manifest, of course, in either case, on cessation of the habit of masturbation or the excessive sexual intercourse.
Another cause of too frequent nocturnal emissions and one wholly separate from any abuse of the sexual function is irritability and mechanical irritation of the sexual apparatus—perhaps especially the membranous and prostatic portion of the urethra—caused by the presence of an excessive amount of oxalates in the urine. Oxalates occur in the urine in sharp angular crystals and would seem to be in a high degree irritating to the tender mucous membrane of the upper part of the urethra. The almost invariable presence of these crystals in excess in those cases that have not been accounted for by abuse of the sexual function leads one to adopt the plausible theory that the crystals are the cause of the irritability. However, we must not lose sight of the fact that these crystals may be simply an accompaniment of the too frequent emissions, and that the presence of oxalates in the urine may be caused by some disturbance in the nutritive processes that go on in the body, which disturbance causes not only the irritability of the sexual apparatus, but also the presence of the crystals.
When the seminal vesicles are much distended it occurs not infrequently that the passage of a hard mass of fecal material through the rectum will, by simple mechanical pressure on the seminal vesicles, force out a few drops, perhaps as much as a teaspoonful, of the contents of the vesicles. This would be called an involuntary emission, but the liquid passed out must not be looked upon as semen. It is simply the secretion of the seminal vesicles, and in losing it, one is not losing a vital fluid or a fluid, any portion of which would be reabsorbed; he is simply losing a fluid which would, in the natural course of events, have passed away within the next few days as a nocturnal emission.
These details have been explained in order that the young man may fully understand the physiology of his sexual apparatus and not be disturbed by the advertisements or the pamphlet literature of charlatans who make a business of frightening young men into the belief that in these experiences they are losing "vital fluid"—that they are victims of "lost manhood," or that they are entering into a condition of "general debility" and "impotence." As an actual fact, involuntary loss of vital fluid (spermatorrhea), is a rare case even in the practice of specialists in genito-urinary diseases, and in these rare cases, the condition is usually a result of very great excesses, sexual debauchery or one of the sequelæ of venereal disease. [Read: Appendix 1, 13 and 17.]
e. Testes. No rational idea of the physiology of the testes can be given without laying down as a fundamental physiological law, that the testes secrete under sexual stimulation only. This same general principle applies to all glands, i.e., that they secrete only under the influence of some special stimulation. In harmony with that law, the testes secrete only under the influence of sexual stimulation.
The sexual stimulation may be sub-divided into two general categories, i.e., conscious sexual stimulation and subconscious sexual stimulation.
Conscious sexual stimulation is partly psychical and partly physical. The physical stimulation is produced by physical proximity of a member of the opposite sex. The physical and psychical phases of conscious sexual stimulation are so intimately interwoven that it is exceedingly difficult to discuss one without constant reference to the other, and it may be said in this connection that the psychical attitude of the two individuals of opposite sex who are brought into close physical proximity will modify very greatly their local sexual responses.
Reverting to the lower animals: when a female in rut or heat is brought into proximity to the male, there seems to be on the part of each animal a consciousness of the character and attitude of the other animal and both animals are step by step excited by various physical contacts and probably also psychical conditions to a high state of sexual excitement, leading to the natural ultimate result, coitus, in which event the sexual excitement culminates in the orgasm of the male, which empties the secreted semen into the organs of the female.
It will be easily understood that, in human subjects whose social relations permit them to indulge in coitus, close physical proximity, and various caresses lead, step by step in the normal course of nature to sexual excitement and sexual desire which culminates as described above for the lower animals.