Testicles.—The function of the testicles is threefold. There is first the inner secretion of certain substances, spermines, which are the cause of the male secondary characteristics. Eunuchs who have been operated upon before puberty show feminine traits in their appearance throughout their lives. They have sloping shoulders, flabby muscles, beardless faces, high-pitched, squeaky voices and festoons of fat on breasts and hips. Secondly, certain stimuli starting from the testicles serve to increase the tonus of the centres of erection. The main function of the testicles is the production of spermatozoa.
Spermatogenesis.—The testicles belong to the class of tubulous glands. The tubules are through the greater part of their course convoluted, tubuli contorti, toward the end they become straight, tubuli recti. The wall of the convoluted tubules consists of three layers, (1) an external connective tissue layer, (2) a middle basement membrane, and (3) interiorly, an epithelial lining. The epithelium consists of two kinds of cells, first the supporting or the sustentacular or Sertoli’s cells and secondly the glandular cells.
When in activity, the glandular cells show three different strata, which represent the three different stages of spermatogenesis. The first stratum, the spermatogones, lie against the basement membrane. They soon begin to increase by cell division and move toward the centre of the tubule. During this movement they increase in size and show the different stages of mitotic division. These enlarged cells are called spermatocytes and form the second stratum. The cells produced by the mitosis of the spermatocytes constitute the third stratum and are called spermatids.
During the transformation of the spermatocyte into a spermatid a reduction of its chromosomes to one-half the number, specific for the species, takes place. This reduction represents the maturition of the sperm-cell, when the segregation of the unit characters is effected. A spermatid is, therefore, already a gamete, i. e., a reproductive cell in the reduced condition.
The spermatids are small round cells which line the lumen of the seminiferous tubules. The spermatids soon become ovoid. The nucleus forms the head, and the cytoplasm is drawn into a tail-like processus. In this stage the spermatids are called spermatozoa. A Sertoli’s cell, together with a group of developing spermatozoa attached to its central end, is called spermatoblast.
The epithelium of the tubuli contorti thus consists of three strata, first of the stratum of the spermatogones, lying against the basement membrane, secondly of the stratum of spermatocytes which are spermatogones in the state of mitosis, and thirdly of the stratum of spermatids which are transformed spermatocytes. The spermatozoa are spermatids which have assumed their permanent shape.
The spermatozoön is divided into three parts, the head, which is the modified nucleus of the male reproductive cell, the intermediate segment, which is the cytoplasm of the cell, and the tail, which is a veritable vibrating cilium, as found in ciliated epithelial cells.
The spermatozoa soon detach themselves from the spermatoblasts and wander into the seminiferous tubules toward the rete vasculosum and epididymis. The spermatozoa possess their own motion. The head is propelled forward by a whip-like wriggling of the tail. The rate of movement is 1.2 to 3.6 millimeters a minute. Water checks the movement and causes the tail to curl up. Concentrated solutions of salts, sugar, albumen and urea may revive the spermatozoa to former activity. Metal salts and acids arrest the movements, while caustic potash and soda invigorate them. Even thin and weak acid solutions, as urine and the vaginal contents,C are harmful, while alkaline solutions are favorable to the spermatozoa. In spermatozoa, which have died gradually after ejaculation, the tail is outstretched or slightly curved, while in those discharged dead, the tail is rolled up in a spiral.
Seminal vesicles.—The seminal vesicles have several functions. The internal secretions serve directly as an excitans of the sexual impulse. The distension of the vesicles reflectorily stimulates the sexual centres. It is a well-known fact that the distention of the vesicles in strict continence gives rise to frequent erections, just as well as the full bladder, constipation, lithiasis, and diseases of the prostate or of the rectum.
The main functions of the vesicles are three in number. The vesicles serve, in the first place, as a reservoir for the testicular secretions. The other function consists in the reabsorption of the unejaculated sperma. The third function is to furnish a fluid for the dilution of the very thick testicular secretion and a medium where the spermatozoa can best carry out their motions.
The seminal vesicles secrete a peculiar mucus, which is thick, fibrinous, glairy, and albuminous. This secretion constitutes the bulk of the semen.
Prostate.—The prostatic gland has a double function. It is the main point wherefrom the stimuli for the sexual impulse start. The internal secretions of the prostatic parenchyma send libidinogenous substances into the blood. The colliculus, rich in nervous elements, sends also out nervous libidinogenous stimuli. The principal function of the prostate is its secretion which imparts to the otherwise sluggish spermatozoa their lively movements.
The secretion of the prostate is thin, milky, translucent, amphoteric or slightly acid. It contains the base spermin which causes the peculiar seminal odor. The secretion gives to the inert spermatozoa their peculiar motion and life.
Cowper’s glands.—The Cowper’s glands secrete a mucous albuminous fluid of alkaline reaction. The secretion takes place before the ejaculation of the semen.
Urethral glands.—The urethral glands secrete a viscid clear fluid. The secretion of these glands, together with that of Cowper’s glands, serve first as a lubricant for the walls of the urethra. The other function is to neutralize the contents covering the urethral walls. The latter are ordinarily bathed in acid urine. This acidity would harm the spermatozoa.
Semen.—The semen is composed of the secretions of the testicles, seminal vesicles, prostatic gland, Cowper’s glands and the urethral glands. The semen is a thick, colorless, gelatinous, opalescent, non-transparent, viscid fluid, resembling boiled starch. It possesses a specific odor sui generis, due to the presence of phosphate of spermin. Its specific gravity is higher than that of water, its reaction is alkaline. It is soluble in water and acids, and is coagulated in alcohol. If it is let stand in a test tube, two layers will be formed, a lower one opaque, consisting of spermatozoa and other cellular elements, and an upper one turbid and translucent, with only a few cells and detritus. The two layers are of about equal thickness.
The semen consists of about ninety per cent. water and ten per cent. solids. Of the solids sixty per cent. are organic substances, thirty per cent. earthly phosphates, and ten per cent. sodium chloride. When a drop of fresh semen is observed under the microscope, it is found full of motion, as if an anthill had been stirred up. This motion lasts for about twelve hours. It is caused by the living spermatozoa. The number of spermatozoa in an ordinary emission, of about ten grammes, is about two hundred to three hundred millions. Besides the moving spermatozoa, there are found a certain number of lecithin globules. Their size is about half the size of a red blood corpuscle. When semen is let stand for a certain time, Boettcher’s crystals, consisting of phosphate of spermin, are formed from the base which gives to the semen its peculiar smell and which is derived from the prostatic secretions. The semen also shows the presence of different kinds of epithelia, the pavement epithelia from the fossa navicularis urethra, the round cells from the prostate, and the columnar epithelia from Cowper’s glands.
Erection.—The male sexual activity consists in the essential features, intromission and ejaculation. For intromission erection is an absolute necessity. The lumen of the vagina is only virtual, there is no real lumen. It follows that only an unflexible body could penetrate into this organ, where the semen has to be deposited for the production of the new being. For this reason, it is prerequisite to copulation that the penis, which is normally in a state of flaccidity, should obtain the required rigidity. This rigidity is gained in the following way.
The tonus, which is present in all the blood-vessels of the body, is the cause that the arteries of the corpora cavernosa penis have only a virtual and not a real lumen. For between the layers of the circular muscular fibres of these vessels is found a layer of longitudinal fibres which narrow the lumen and almost entirely compress it.
When the tonus relaxes, the blood precipitates into the enlarged vessels and the cavernous spaces, and an active increase in the amount of arterial blood is the result. Through the increase of the lumen of the arteries and caverns, the veins are compressed and the blood cannot flow out of the cavernous bodies. Thus the active increase of arterial blood serves as a check of the reflux of the blood through the veins by the pressure of the distended arteries and caverns upon these veins. Besides this check, the vena profunda cummunis, by which the blood of the corpora cavernosa penis has to return, passes through the unstriped muscular fibres of the musculus transversus perinei profundus. Now, this muscle contracts synchronously through the same influence of the nervi erigentes which caused the relax of the tonus in the arteries. The contraction of the muscle causes the compression of the vena profunda and prevents the blood from flowing off. Besides the muscular transversus perinei, the musculus ischio-cavernosus which arises from the os ischii and encircles the radix of the penis, as well as the musculus bulbo-cavernosus by compressing the bulbus urethrae will, both, at their contraction, prevent the blood from flowing off. In this way there is not only an active increase in the amount of arterial blood, but also an abrupt decrease in the amount of venous blood, flowing out of the penis. The corpora cavernosa, therefore, become of almost cartilaginous hardness, and the penis reaches the state of rigidity, necessary to the performance of the male sex-act. When erection is complete the contraction of the musculus erector penis draws the organ up against the abdomen and gives it the same direction as that of the vagina.
Colliculus.—With the erection of the corpora cavernosa, the colliculus also swells and almost fills up the entire lumen of the prostatic urethra. In this way the bladder which has already been closed by the contraction of the sphincter, is closed up more tightly, so that not a drop of urine could escape. The erection of the colliculus also causes the orifices of the ejaculatory ducts to take the direction forwards toward the pars membranacea.
Urethra.—At this stage the urethra obtains an actual lumen. Through the net of veins which surround the mucous membrane of the urethra and through the turgescence of the corpus cavernosum urethrae, the canal of the urethra opens and remains gaping through the entire duration of the erection. In this way it is admirably fitted to give a free passage for the semen. In the mean time the urethral glands are constantly secreting their viscid clear fluid, which, together with the secretion of the Cowper’s glands, provide a lubricating and protecting coat for the urethra and neutralize the contents of the urethral walls which are otherwise bathed in acid urine.
Ejaculation.—The last important step of the male sexual act is ejaculation. The spermatozoa leave the lining of the tubuli contorti and wander through the tubuli recti to the rete vasculosum and hence through the vasa efferentia to the head of the epididymis. They continue their wanderings through the epididymis and vasa deferentia until they reach the seminal vesicles and the ejaculatory ducts. During sexual tranquility and in a normal state of health, the ejaculatory ducts, owing to the narrowness of their diameter and the oblique direction of their orifices, are sufficiently compressed to prevent the semen from reaching the urethra. The semen, therefore, remains in the seminal vesicles until needed for ejaculation. If not needed in due time, it is, as a rule, reabsorbed, and the overflow, if there be any, is discharged during sleep, accompanied by libidinous dreams.
Coincident with erection the entire situation changes. Before ejaculation the testicles are forcibly drawn up to the external rings of the inguinal canal, by the action of the cremaster muscle. Through the contraction of the epididymis and the coni vasculosi, the seminal fluid is propelled toward the vasa deferentia. Through the peristaltic movement of the vasa deferentia and the seminal vesicles, the semen is pressed into the ejaculatory ducts. The latter, by means of the muscular layer in their walls, forward the semen to the prostatic urethra. The action of the ducts is at this moment facilitated by the changed direction of their orifices. The change takes place through the turgescence of the colliculus. The swelling of the colliculus and the contraction of the external sphincter of the bladder prevent the semen from flowing backward into the bladder.
At this stage the muscular substance of the prostate contracts and squeezes out the prostatic fluid into the urethra. The fluid had been stowed up in the follicles until there was a demand for it. All these secretions of the testicles, seminal vesicles, and prostate, meet synchronously in the prostatic urethra and are there temporarily stowed up.
The muscular layer which surrounds the membranous portion of the urethra is a veritable sphincter, the contractions or dilatations of which will propel or retain the semen. The semen pouring from the ejaculatory ducts and the secretion of the prostate are steadily forced forward. But, retained by the contracted sphincter externus, the semen is forced into the bulb of the urethra, as the place of least resistance. In this way the bulbous part of the urethra becomes distended and serves as a temporary reservoir for the semen before ejaculation. By reflex excitation, this distention causes spasmodic contractions of the musculus bulbo-cavernosus and clonic contractions of the accelerator urinae. The contractions of these two muscles overcome the contractions of the sphincter, i. e., the muscular layer of the membranous portion of the urethra, and the semen is driven forward and gushes out of the meatus, in several jets, through the open and well-lubricated canal of the urethra.
Nervous control of erection.—The mechanism of erection and ejaculation is controlled by six centres, the three cerebral, one in the medulla oblongata, and the two spinal. Erection may be caused by the stimulation of the cerebral centre of voluptas. Impressions originating in the brain, as sexual thoughts, may evoke vigorous erections. There is no function of the human economy over which the mind exerts a more powerful influence than over that of sex. The imagination, says Hammond, is always a more potent stimulant of sexual desires than the physiological incentive supplied by nature. Besides by imagination, the cerebral centre may be excited by impressions conveyed through the senses. Sight, smell, hearing, and in some pathological states even taste are well known to convey sexual stimulation to the brain. The sense of touch has such an influence over the generative function that it is considered the inseparable companion of sexual activity.
Erection may further be stimulated by excitation of the centre in the spinal cord. The direct electrical excitation of the spinal cord in dogs evokes vigorous erections. The irritation of the spinal cord in some spinal diseases often produces erections. Sleep, while lying on the back, is known to produce vigorous erections, by increasing the flow of blood to the spinal cord and by allowing the blood to settle in the medulla oblongata and in the cord, so as to produce a passive congestion.
Erections may finally be evoked by the stimulation of the peripheral nerves at the genitals as on the glans and on the skin of the penis. Especially the prostatic urethra and the colliculus are recognized as the most sensitive area, the focal point of the nervous impressions on the genital system. Pressure of the metal sound on the prostate or its cauterization, tumors, calculi and inflammations, e. c., gonorrhoea, may often excite erections. The prostatic mucous membrane is supposed to be the seat of the pleasurable sensations. During any kind of sexual activity, the prostatic area is intensely congested, and its nerves are in a high state of tension. Excitations at the neighboring parts of the genital organs, as evoked by hemorrhoids, stone in the bladder, full bladder, worms or full rectum, may also produce erections.
The peripheral excitations of the genitals are transmitted to the central nervous system, i. e., the centres in the pons and in the medulla, by reflex action. From these centres the stimulus is conveyed to the centres of erection in the lumbar region. If the individual is in a state of unconsciousness as in sleep, the stimulus at the periphery takes the direct road to the centre of erection. The excitation of this centre is then carried by the way of the nervi erigentes to the corpora cavernosa.
Centre of inhibition.—All the nervous elements, the cerebral centre of voluptas or sex-desire, the spinal centre of erection, and the nerves at the periphery, not only at the genitals, but the nerve endings of the skin through the entire body, work in perfect harmony. Hence a man in full vigor of virility would have vigorous erections at the slightest touch or even sight of a comely woman. Given our present mode of life, with the ubiquitous opportunities for such sights at all times, normal healthy men would have to walk around on the streets in a state of permanent priapism, but for the cerebral centre of inhibition. The influence emanating from this inhibitory centre works upon the spinal centre to prevent erection. When the influence of this centre is removed, erection is facilitated. When the spinal cord of a dog is severed in the lumbar region, the irritation of the genitals more readily provokes erection. With the removal of the inhibitory influence during sleep, the least excitation of the genitals causes vigorous erections. When the stimulation of the inhibitory centre is unusually increased, as in neurasthenics and other nervous disorders, erections fail to appear, when they are most desired.
Thus, by the inhibitory action of the brain, the tonus of the centre of erection preserves the equilibrium, and it requires longer preparations and more intense excitations than is ordinarily furnished in social intercourse to evoke erections, necessary for the performance of the sexual act. When cerebral inhibition is removed, as in sleep, erections are facilitated. On the other hand, when the inhibitory influences are increased, as in a state of intense mental occupation or of depressing emotion, as fear of inability to consummate the act, or fear of detection, or at the loss of the object of one’s affections, or in cases of extreme modesty or disgust, etc., erections may be prevented or entirely arrested. Hence the normal accomplishment of the sex-act requires complete absence of doubts, apprehensions, of any anxiety whatever, and want of confidence in one’s own power. Otherwise the inhibitory influences will prevent a perfect erection.
Centre of ejaculation.—The centre of ejaculation has its seat in the level of the fourth lumbar vertebra. In a state of perfect health, the excitability of this centre is much lower than that of erection. Hence it requires more intense stimuli and longer preparation to produce an ejaculation than an erection. The best stimulus for this centre is the tender, soft, warm vaginal mucosa, when rubbing against the glans and the skin of the penis.
Orgasmus.—The complicated reflex nerve phenomena taking place in a complete and perfect male sexual act may be described as follows:
At the first voluptuous thrill of a physical pleasurable sensation, and at the first tactile excitation of the sensual organs, the cerebral centre of inhibition is at once paralyzed and its influence is removed. The centre of erection has now opportunity for the full display of its vasodilatory influences. The tonus of the genital vessels is removed, and an increased amount of blood flows into the arteries and caverns so as to render the penis stone hard. Through the increased blood supply and under the greatly increased nervous tension, the genital glands, the testicles, seminal vesicles, and prostate secrete an increased amount of their respective fluids. These secretions pour into the urethral bulb and distend the same. The excitations, radiating from this distension, serve to stimulate the centre of ejaculation, and the contractions of the muscles bulbo-cavernosus and accelerator urinae take place. The result of these contractions is the phenomenon of ejaculation.
Simultaneously with the ejaculation, the nervous tension, which was increased to the highest degree through the excitations of the different organs, is also removed. This explosion of the nervous tension during the crisis produces the pleasurable sensations which are known under the name orgasmE (from the Greek word ὀργᾶν, to swell with lust).
After ejaculation and the removal of the genital congestion, the paralysis of the inhibitory centre ceases, and the normal nerve tonus of the blood vessels gradually reappears. The influx of blood into the genital vessels is thus cut off, and the erection of the corpora cavernosa ceases. Only the colliculus remains yet swelled, for some time. For this reason micturition is impossible immediately after ejaculation. After the act follows a state of exhaustion, weariness, weakness and inclination to sleep. Although the frantic condition and the semi-delirium generally lasts a short time only, still it is sufficiently long to exhaust completely the strength of the ordinary organism. After a certain time of rest, sex connection in a healthy person is followed by a joyous feeling and fresh vigor. The head feels more free and easy, the body more elastic, and a greater disposition to physical and intellectual labor results.