According to recent views, all the ova are formed during the embryo nal period, and an increase of these does not occur. The number of those ovules, according to the investigations of Sappey and of Henle, is an un usually large one. Since, at a given moment in the puberal period, the number of follicles is a relatively small one, a large number of follicles must remain in their incomplete form (cell-aggregations without fluid) even after puberty. But as the demand for ova, in comparison to the number of these incompleted follicular rudiments, is a very small one, the greater part of this follicular foundation with its ova must become destroyed in the stroma of the ovary sooner or later. In fact, the re mains of such destroyed follicles are found partly as folded membranes, partly as fattily degenerated masses. Only a small number of ovules are therefore of use.
While, therefore, the foundation of the ovary is completed before birth, there appears after this a period of rest. Even though here and there small vesicles are met with in the ovary during childhood, the further development of the follicular apparatus does not proceed until the ap pearance of puberty, and only with the completion of this is the ovary to be considered as fully developed. At this time, that position, form and appearance, which we look upon as normal, shows itself. The proper function of the organ now begins: the maturing and extruding of the ovules formed coincidently with the ovary. This process is, according to the present view, not a continual, but a periodical one, which occurs principally in the follicles. Under the influence of a congestion of the genitals, usually recurring every four weeks, there is a marked increase in the fluid contents of a number of follicles; still, as a rule, only one ovum is thrown off in the course of a lunar month. One of the fol licles, enlarged by a previous congestion, approaches the surface of the ovary by the further increase of its fluid contents, and the stroma, which lies between the wall of the vesicle and the epithelial cover ing, is at first thinned and then disappears altogether, so that the follicular wall causes the surface of the ovary to arch forward. Hereby the most prominent part of the wall, which is free from the net work of blood-vessels which surrounded the follicle, also undergoes a marked thinning. By the increase of this pressure exerted by the fluid contents, that part of the follicular wall which projects -into the abdominal cavity is ruptured. It is also possible that the smooth muscu lar tissue contained in the stroma, increase, by great tenseness, the pres sure in the follicle and assists in its rupture. But it is not probable that
an extravasation of blood into the Graafian follicle assists: the rupture of the vessels occurs probably after the emptying of the follicle, and is caused by the sudden diminution of the forcible intra-valicular pressure. The fluid of the follicle is now emptied through the opening, and the ovum— which usually, but not always, lies on the side opposite to the rupture, and is, with its surrounding cells, forming the so-ealled discus proliferus, already loosened from connection with its foundation—is, with the discus oophorus, carried into the abdominal cavity.
The change which the ruptured follicle undergoes is somewhat dif ferent, according as to whether the extruded ovum is impregnated or not. After the escape of the fluid contents, the opening is closed by the formation of a delicate cicatrix; the membrana granulosa, consisting of epithelial cells, arranges itself in folds, which enclose a small quantity of pure blood. In place of the resorbed blood, yellow masses appear, which consist of yellow pigmented, granular, multiformed cells. Whether these arise from wandering white, blood-corpuscles, or whether they arise from a luxuriant growth of the cells of the membrana granu loss is not certain. Coincidently, connective-tissue processes are sent out from the enveloping membrane of the follicle, which attach themselves at about the centre of the vesicle and which carry blood- and lymphatic vessels, and which e,ause the later cicatrization of the changed follicle. In the impregnated female, under the influence of the permanent conges tion of the genitals, the former follicle, which on account of its in tensely yellow color is called the corpus luteum, and which shows greater dimensions than the follicle from which it originated, remains until the termination of the pregnancy; then the yellow masses disappear and a true nodule, the corpus albicans, is formed by the production of connec tire tissue. If the blood-vessels are destroyed, the coloring matter of the blood is liberated, and this small body is given a blackish hue, the corpus nigrieans. This formation is then forced into the interior by the en largement and advancement of other follicles to the surface, and is then later on completely destroyed. Much less intense and of much shorter duration is the retrogressive metamorphosis if conception has not resulted. The body remains small, does not exhibit any yellow color and soon dis appears. This process just described, is, in its entirety, 'called ovulation.