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.
CUT XXXII.
Normal sperma.
1, Boettcher’s crystals; 2, amyloid bodies; 3, hyaline bodies; 4, testicular cells; 5, urethral epithelia; 6, lecithin bodies; 7, 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.