THE SEMEN.
The semen is secreted by the testicles, accumulated in the seminal vesi cles, and thrown into the urethra by the ejaculatory ducts. From there it is carried directly into the genital organs of the female by the emission which finishes coition.
It is a white, viscous liquid, with a density much greater than water, and the consistency of which increases by continence. By desiccation it stiffens when it is deposited, and it has a peculiar odor like the raspings of bone, or the flower of the chestnut-tree. Some authors hold that this odor does not really belong to it, but is due to the mixture of liquids from the glandular apparatus of the prostate and urethra.
This liquid consists of water, extractive matters, and phosphate and chlorhydrate of lime and soda, but it is characterized by the presence of peculiar organisms discovered under the microscope.
When the semen is examined with the microscope, there are found pavement epithelial cells, cylindrical cells, spherical nuclei, leucocytes, crystals of magnesium phosphate, special bodies called spermatozoids or spermatozoa, or zoospermes, according as they arc considered as belonging to the animal or vegetable kingdom.
These spermatozoa were discovered in 1667 by Louis Hamm, a medical student, and were especially studied by Leuwenhoeck, who wrongly claims the honor of their discovery. They are animated filaments with an action of their own, and form the essential fecundating part of the semen. They are about thth of an inch in length, formed like the tadpole of the frog, and have three parts, head, body, and tail. (Fig. 68.) The head is the smallest part. Its length is about one twentieth of the length of the tail.
The body is small, oval, and flat, immediately behind the head, with which it is almost blended.
The tail is filiform, thicker at its beginning, becoming almost impercep tible at its end.
Ordinarily, plainly separated from the body and the head, it is some times covered by a little projecting pad, which is only the remains of the nucleus in which the spermatozoid is developed. Godard and Liegeois
discovered besides these normal spermatozoids, another variety with a smaller head.
These little bodies are animated by very rapid movements, and can cover a distance nearly equal to the length of their bodies in a second. These movements generally stop in about twenty-four hours after the semen is exposed to the air. Placed in a closed jar the spermatozoids still move at the end of fifty to sixty hours, and, deposited. in the genital organs of a woman, seem to keep an extraordinary vitality, for Percy is said to have found them alive on the cervix of the uterus of a woman eight days after the last coition. This vitality lasts even after the death of the individual, for Godard proved it seventy-two hours after death by execution. They are more or less abundant according to the individual, and the fecundating property of the semen seems to be much more active when they are more numerous and animated by more movements. But their absence in the semen does not fatally involve impotence, as Casper, Hirtz and Montegazza believed. The individual, in this case, can accomplish coition, but the coition is fatally non-fecundating. High temperature stops the move ments of the spermatozoids, but these movements can be reproduced when the temperature is brought to 98.2° F. They are definitely de stroyed by the electric spark, alcohol, acids or alkaline fluids too highly concentrated. The alkaline or acid state, exaggerated by the vaginal or uterine secretions again acts on them fatally; the menstrual discharge on the contrary increases the movements.
Up to sixteen or seventeen years the semen does not contain spermato zoids, but after this age they are always found in normal semen; it is only in very old men that they are no longer found, for the researches of Duplay and Dieu show that in old men of seventy-five or eighty years they are in most cases still found.