Fig. [12].—Female external genital organs of a virgin, attached to the vagina which has been isolated and opened, and a portion of the cervix uteri, Hymen, etc. (From Toldt: Atlas of Human Anatomy.—Rebman Company, New York.)
Fig. [13].—The external genital organs of a virgin, drawn apart transversely (after von Preuschen). c. Clitoris. f. c. Frænum of the clitoris. n. Nymphæ. l. Labia majora. o. u. Urethral orifice. h. Hymen. f. n. Fossa navicularis.
The infantile uterus is so proportioned that its neck (collum vel cervix uteri) constitutes the larger part of the organ, as much indeed as two-thirds. Owing to the small size of the body (corpus uteri), the whole uterus is very flat, and its borders ascend in a direction almost parallel to each other, diverging somewhat abruptly into the Fallopian tubes, recalling in some degree the two-horned embryonic form of the organ (uterus bicornis). The plicæ palmatæ on the surface of the cervical canal, which make up the arbor vitæ uterina, are strongly developed; the median longitudinal ridge bifurcates, and its divisions can be traced on either side into the uterine orifice of the Fallopian tube (ostium uterinum tubæ). The lips of the vaginal portion of the cervix are comparatively speaking very large and terminate in sharp angles. The vaginal mucous membrane is everywhere beset with long papillæ. The development of the uterus shortly before puberty consists chiefly in the enlargement of the body of the uterus, and the growth of its walls in thickness.
Fig. [14].—Sagittal section of the female pelvis (after Breiolei).
At the time of puberty, according to Toldt, the body of the uterus in the virgin has already increased till its length is half that of the entire organ; and at the first appearance of menstruation the body and neck of the virgin uterus are nearly equal, with perhaps a slight preponderance in size of the cervix, and the walls of the uterus have become convex. In consequence of this change the organ becomes pear-shaped, and the uterine cavity (cavum uteri) assumes the form of a triangle with moderately incurved sides. The cervical canal becomes wider in the middle; the margin of the os uteri becomes smooth and rounded. The walls of the virgin vagina are marked with numerous dentate transverse ridges (rugæ), especially near the lower end and on the anterior walls, the columns of the vagina (columnæ rugarum), from which the transverse ridges run to either side at right angles, extend half way up the vagina, and are of a hard consistence.
The characteristic changes in the ovary at the time of the menarche originate in the changes undergone by the ovarian follicles. A large number of small separate follicles is to be found already in the ovary of the new-born infant. These structures, known as primitive follicles, are formed by detachment from the egg-tubes that grow down into the stroma from the superficial germinal epithelium; they are spheroidal vesicles, enveloped by a single layer of cubical cells, and their interior is entirely filled by the primitive ovum or egg-cell. This latter consists of very finely granulated protoplasm with spherical nucleus and distinct nucleolus, but no trace of an investing membrane can as yet be discerned. The further development of the ovarian follicles takes according to Toldt the following course: A rapid multiplication of the cubical cells that form the wall of the follicle occurs, so that the ovum is surrounded by two, three, or several layers of cubical or rounded cells, and the whole follicle gradually increases in size. At the same time the ovum assumes an eccentric position in the interior of the follicle. At or near the middle of the follicle a slit-shaped space now appears, filled with a clear colorless fluid. As this space gradually enlarges, the follicle[[19]] becomes converted into a vesicle filled with fluid, the wall of which is composed of small cubical cells. Simultaneously with the growth of the follicle a lamination of the elements of the surrounding stroma takes place, so that a somewhat sharply defined capsule is formed. In this condition these glandular structures of the ovary are known as graafian follicles.[[19]]
Before puberty, these graafian follicles are small vesicles of a diameter of one to two millimetres, containing the large unicellular ova. Each of these consists of an envelope, the zona pellucida (also known as the zona radiata, or striated membrane of the ovum); an external granular mass of protoplasm, the vitellus or yolk; a vesicular, spherical nucleus, the germinal vesicle; and a nucleolus, which if single is large and prominent, the macula germinativa or germinal spot. As early as the second year of infancy every imaginable intermediate stage between the primitive follicle and the fully-developed vesicular graafian follicle can be observed.
At the time of puberty certain larger follicles are always to be distinguished, which have moved inward toward the interior layers of the ovary, whereas the smaller follicles have a more peripheral situation; thus, according to Waldeyer, we observe at this time in a section of the ovary, proceeding from without inward, first the epithelium, next the fibrous tunic, next the zone of younger follicles, and finally the zone of older follicles. According to Henle and Waldeyer, at the commencement of puberty, there are in each ovary about 36,000 ova, giving a total for the two of 72,000.