organs are concerned with such life-history of the egg, and really exist merely to create such a history, or rather, to produce the process which constitutes the basis of such history.

The ovum, or egg, when discharged from the ovary, is at first surrounded by a few cells which serve as nourishment, but which soon disappear. It enters the Fallopian Tube and begins its journey toward the Uterus, being urged on its way by the constant movement of the lining-cells of the interior of the tube, in the direction of the Uterus. Certain changes in structure occur. Its passage to the Uterus may be interrupted, and the ovum lost and finally cast off. But the ovum that is successful finally arrives at the Uterus where it awaits impregnation or fertilization by the spermatozoon of the male.

If copulation occurs within a reasonable time after the arrival of the ovum, it is impregnated or fertilized. Fecundation results and conception ensues, the ovum then remaining attached to the walls of the Uterus, and in time develops into the foetus. If, however, the ovum is not impregnated, because of absence of copulation or from other causes, it gradually loses its vitality, and is finally cast off with the several uterine secretions.

It should be explained here that the "spermatozoon" of the male (the plural of the term is "spermatozoa") is the male generative "seed." The sperum, semen, or seminal fluid of the male is filled with hundreds of thousands of spermatozoa. Each spermatozoon is a minute living, moving creature, resembling a microscopic tadpole. It has a head, a rod-like body, and a thin hair-like tail, the latter being kept in constant motion from side to side, by means of which the tiny creature is enabled to travel rapidly from one point to another. The human spermatozoon measures about one six-hundredth of an inch in length. It is composed of protoplasm, the substance of which all living creatures are composed. The spermatozoa are believed to be developed from a parent sperm-cell, by the process of segmentation or subdivision, which process is common to all cell-life. The numerous spermatozoa dwell in a gelatinous substance, which, mingling with the other fluidic secretions of the glands of the male, constitutes the male seminal fluid, sperm, or semen, which is ejaculated by the male during the process of copulation.

Fecundation (i. e. fertilization, impregnation; the process by which the male reproductive element is brought in contact with the female ovum or egg) is brought about by the blending of the male reproductive element (or spermatozoon) with the female reproductive element (or ovum, or egg). This blending is of course accomplished by the bringing together in mutual contact the two reproductive elements just mentioned. The sexual act which results in this "bringing together" of the two elements is known as "copulation," or "coition." In copulation or coition the seminal fluid of the male, containing an enormous number of spermatozoa, is ejaculated from the male intromittent organ into the receptive canal or channel of the female (the Vagina), and in this way finally comes into actual contact with the female ovum or egg which is awaiting it in the Uterus of the female.

The spermatozoa (in the process of copulation) are deposited in the Vagina of the female, usually at its upper end, but sometimes in the lower portion; and in rare and peculiar cases even at or about the Vaginal Orifice or outer vaginal opening. In either case they travel up the remaining portion of the Vagina and finally enter the Uterus or womb. The spermatozoa possess wonderful vitality and power of locomotion. There are cases recorded in which the spermatozoa deposited on or about the outer female genitals have managed to travel inward and upward until they have finally reached the Uterus, where conception has resulted. Such cases, of course, are rare, but they exist, well authenticated and accepted by medical science as facts.

It must not be supposed, however, that the impregnation of the ovum occurs only in the womb proper. Cases are known in which the spermatozoa have traveled along the Fallopian Tubes and impregnated the ovum there; and in very rare cases the spermatozoon seems to have penetrated even to the Ovary itself, and there impregnated the ovum on the surface of the Ovary. Some excellent authorities, in fact, insist that all normal impregnation occurs at the end of the Fallopian Tube—the point of its entrance into the upper part of the womb, rather than in the body of the womb, or at its mouth, as the older authorities taught. But wherever the actual contact of spermatozoon and ovum occurs, the blending of the elements is performed and fertilization, impregnation, or fecundation is accomplished.

As a result of copulation, then, the spermatozoon (or a number of spermatozoa) comes in contact with the female ovum or egg. Then one or more of them, by means of a furious lashing of the tiny tail, manages to penetrate the outer covering of the ovum, and enters the space between the outer covering and the real body of the egg. Several spermatozoa may effect an entrance into this outer space, but only one is permitted to enter the real body of the egg. [Twins are produced by the impregnation of two ova by two spermatozoa, at the same time. The presence of the two ova at the same time is unusual]. The moment that the real body of the ovum is penetrated by the successful spermatozoon, a tough covering or thick membrane forms around the ovum and thus prevents the entrance of other spermatozoa. The successful spermatozoon then loses its tail, and the remaining head and body become what is known as "the male pronucleus."

The authorities are uncertain as to the exact nature of the change which occurs when the ovum is penetrated by the spermatozoon. The outward manifestations of the change and transformation arising from the blending of the male and female elements are of course well known, but the "life process" eludes the power of the microscope. When Nature forms the thick membranous coating over the impregnated ovum, she draws the veil over one of her most important secrets. The first segmentation-nucleus having been formed by the blending and forging together of the male and female pronuclei, the process of segmentation begins.

Segmentation proceeds as follows: the impregnated egg splits into halves, forming two joined cells; then into quarters, forming four joined cells; then into sixteenths, then into thirty-seconds, sixty-fourths, and so on, until the ovum consists of a combined mass of very minute granular-like cells, the whole resembling a mulberry. The segmentation of the nucleus precedes and then continues with the segmentation of the yolk. After the egg has been divided into a great number of these cells, the latter begin a centrifugal action resulting in the formation of a complete inner lining of closely packed cells, with a central cavity filled with the yolk liquid.

In the meantime, the Uterus has been prepared for the reception of the impregnated and transformed ovum. A thick, spongy, juicy, mucus membrane forms, into which the changing ovum passes and attaches itself; the mucus membrane soon enveloping it and shutting it off from the rest of the Uterus. There now appears at one point on the ovum an opaque streak, which is called "the primitive trace" of the embryo—the first beginning of the young living creature. The "primitive trace" then grows in length and breadth. At this point we must leave the history of the ovum, or human egg, for the present; its further development will be related in the succeeding lesson, the subject of which is "Gestation."

LESSON IV
GESTATION OR PREGNANCY

Gestation is