NOW that we have thoroughly discussed the other two secretory functions, we come to the real object of our study: the seminal secretion, apparently the least important of the three secretory functions which are localised at the lower pole of our body, but really the most important by reason of its ultimate effects and the phenomena which accompany it. But the reader who has had the patience to study the other two secretions, has now gained a correct insight into this function.
If, however, a thorough description of the seminal secretion is still required, read the last chapter over again carefully; but read semen instead of urine, seminal vesicles instead of urinary bladder, and seminal ducts instead of ureters. The seminal secretion with all the normal and abnormal influences which act as stimuli, follows the same scheme as the urinary secretion.
Just as in the urinary bladder, the antagonism is only caused by the volume, the distension; it makes no difference whether the semen contains a great number of sperm-cells, or none at all. So we see how erroneous were the old ideas that the spermatozoa could excite erection by the liveliness of their own movements. This is so far from being the case, that this independent movement does not occur until they can move in a thin fluid menstruum. The following explanation will make clear why we have two seminal vesicles but only one urinary bladder. In the period of embryonic life when the anterior abdominal wall was still quite open, not only the primordial kidneys, but also their excretory canals were two separate ducts leading to the genital eminence. But later, when the abdominal wall was closed almost to the umbilicus, simultaneously with the formation of the umbilical cord, a single unpaired urinary bladder composed of a single cavity, and consequently a single unpaired urethra, was formed.
Functionally, however, there is no essential difference; as a general rule both the seminal vesicles contract simultaneously (1) and separately only under the influence of very slight stimuli.
Because the semen is ejaculated from two seminal vesicles, it may be imagined that it will be ejected with greater ease and force. This, however, is not the case, as the two excretory ducts of the seminal vesicles, and especially their openings into the urethra, are so extremely fine, because really they are. only embryonic excretory canals, that even the most powerful contractions of the seminal vesicles are scarcely able to force the semen into the urethra.
It is very significant that these two apertures should be so extremely small, much smaller than the two seminal ducts. Because the two seminal vesicles are only laterally attached to their ducts it may happen (in contradistinction to the urinary apparatus, in which both the ureters discharge into the bladder itself), that sperm cells simply pass by the seminal vesicle without entering it. In this manner it might only too easily happen that semen would escape with urine unnoticed, without exercising its fertilising function, as is sometimes the case in serious paralytic conditions (spermator-rheaseminal emission without erection). But the extreme fineness of the two apertures in itself causes a resistance as elastic as the best occlusory muscle. So the antagonism in connection with the secretion of semen is unmistakable, even for those sperm-cells which have not penetrated into the seminal vesicles.
The problem of the ejaculation of the semen is rendered very much more difficult, because on account of the small volume of these organs and their concealed situation, the utility of abdominal compression must be inconsiderable. Instead of this Nature employs a far more efficacious method, so that when finally the antagonism has reached a spasmodic culminating point, it can accomplish the final evacuation in a surprising manner, which will be fully discussed in Chapter 21.
Our seminal apparatus, however, had developed but little since the beginning of the embryonic period; but in this case congestion is paramount. For this reason erection is such a typical phenomenon of the sexual life.
The periodicity of the secretory manifestations is, as we have already explained in Chapter 15, dependent on the volume of the substance to be voided; the greater the volume, the shorter the periods between the excretions.
In this respect it is worth while comparing once again the seminal secretion of the male and the egg secretion of the female organism. If the quantity to be excreted by the male is small, it is surely reduced to a minimum in woman: only one solitary almost microscopic egg-cell.
In conclusion, as we must go a little more closely into the details of periodicity in both sexes, I will make a few practical remarks on the subject.
The age at which the sexual secretion begins to appear, is termed in both sexes the age of puberty. In girls the first traces of menstruation generally appear at from 13 to 15; in tropical races this happens much earlier, but in Germany and Holland frequently much later, especially in the country. This occurrence is repeated regularly at intervals of from 3 to 5 weeks; in anaemic girls fortunately less frequently and less profusely.
In the youth at from 14 to 16 years of age, the first traces of emissions occur during sleep, and these are repeated once or more each week as long as he remains sexually abstinent, antagonism reaching consciousness by means of erections. As far as no external, more accidental, influences make themselves felt, the erection-curve runs more or less parallel with the emission curve. As often as the seminal vesicles and canals have emptied themselves or when this has occurred say twice at a relatively short interval, it may happen that under influence of the recent experience, erection will recur with redoubled strength; but if one does not give way to it, there at once sets in for a shorter or longer time, a relatively, if not completely, calm period, until the seminal vesicles are gradually once more subjected to high pressure.
It also happens in the males of the lower animals that when copulation and masturbation are impossible, the seminal fluid is finally spontaneously ejected, especially during unsuccessful attempts at mating.
It is less commonly known that it may happen exceptionally in the female organism that the typical feeling of sexual satisfaction, with its congestive pulsations, is very distinctly experienced, either during sleep or in a half-dreaming state at night; in the daytime this only occurs as the result of a powerful extra-genital stimulus; e.g., a very passionate kiss.
There is absolutely no cause to worry about our nocturnal emissions, as long as they only happen in sleep, even if they are accompanied by vivid dreams. At most, if they occur too frequently, they leave a psychic depression as a symptom of fatigue. For the sexual function occasions in both sexes a deep agitation of the nervous system, which may be manifested in the most varied ways, particularly in the psychic sphere.
Woman arrives at the end of her functionally active sexual life at about 50 years of age, after the secretion has gradually become less frequent and profuse. Amongst tropical races, where puberty commences earlier, old age also sets in earlier. This time of life is known as the climacterium. We should not be surprised that in the female, although youthful and active in other respects, this function ceases at an early age, if we consider how difficult it is for the egg to force its way through the ovarian tissue, and how this difficulty must increase with advancing years, as the ovarian tissue loses its elasticity and becomes harder and firmer. But for copulation the climacterium (or change of life) is no hindrance; on the contrary it removes all danger of pregnancy. It is only with very advanced old age that the possibility of copulation is lessened and finally excluded, because the mucous folds become too stiff, and vulva and vagina appear to be too constricted.
In man, however, even when he is old, the sperm-cells which are constantly forming afresh can be so easily excreted that this secretion only becomes gradually limited with most advanced age, and no limit can be assigned. But what otherwise would be the most effectual stimulus to erection will then be found useless. At any rate sooner or later relative impotence may set in through diminished power of response to stimuli.
When a married person has regularly practiced sexual intercourse, and this is suddenly interrupted by the death, illness or absence of the partner and not resumed, there often elapses a considerable interval before nocturnal emissions reappear; a striking proof of how powerful the impulse must have been before the spontaneous emission occurred.
If one is troubled with too frequent nocturnal emissions, e.g., if they occur every night, he should consult a physician who can no doubt prescribe hygienic measures without resorting to drugs. Emissions only seriously threaten the health if they occur in the daytime: and it is worse, if they occur, as for instance in advanced age, without erection, just as the urine may drip away through paralysis of the occlusory muscle (sphincter).
1 Although the seminal vesicles lie closely pressed against the bladder, one on either side, the urinary bladder and the seminal vesicles never function simultaneously, any more than at the upper pole of the body swallowing and breathing take place simultaneously. This last does not happen, because when swallowing food, the epiglottis bends downward and so bridges over the windpipe at the opportune moment. And in the same way each time that the seminal vesicles with their occlusory muscles are stimulated, the erection thus occasioned immediately constricts the urethra to such an extent that the voiding of urine is almost impossible. If that were not so, and if the urine were voided along with the semen, as is the case in serious conditions of impotence, the semen would always be washed away with the urine without being able to cause fertilisation.