ANATOMICO-PHYSIOLOGICAL INTRODUCTION.
And while in the human embryo the union of the MiiHenan ducts takes place at a very early period, and is completed ac cording to Dohrn by the ninth week of embryonal life,' the differentiation of the simple genital canal into uterus and vagina does not occur until much later. Kussmaul places it at the end of the third month; though Dohrn ° could not appreciate tbe existence of a cervix until the fifteenth or sixteenth week. The lower edge of the tube, which later bears the hymen, is found where the genital canal opens into the sinus uro-genitalis. The hymen does not appear before the beginning of the nineteenth week, and is at first a simple projection of the posterior wall from the introitus; soon a smaller process from the anterior wall unites with it to form the half-moon fold.° We will follow Dohrn, who thus describes the vaginal changes: only after the portio vaginalis is fully formed does the smooth-walled genital canal undergo change. Longitudinal growth is rapid during the seven teenth to nineteenth weeks, and the redundant internal coat is forced into tranverse folds, which interlace with one another. At the same time the upper part of the vagina dilates, while its lower portion to the extent of -213th to irth inch, contracts markedly. At the end of that period, a papillary growth appears in the vagina, especially in its middle portion.
Above these, papillte continue to the vaginal portion of the uterus, and below they extend to the raphe of the sinus uro-gen tails. They are found upon the upper surface of the hymen only; the lower surface and the vestibule being smooth. One week after the first appearance of the hymen it is as fully developed as is usual in the newborn. After the lower portion of the vagina has been almost closed by the hymen, its in ferior section dilates, and is limited above by a projecting fold, which may be mistaken for a second hymen. In newborn females the vagina is a relatively wide and long tube, the lower portion being partly closed by the hymenal fold. The structures of its wall and the papilla3 are well devel oped, and an abundant layer of desquamated epithelium is present. Ac cording to Huschke,' the relative length of the vagina to the entire body is as 1:9, while in the adult it is as 1:15.
Freund ' and Hocks ' have recently reopened the question as to the !per sistency of the remains of the Wolffian duct, the Gartner canals. They have described a case in which there were two small openings correspond ing to the mouths of these canals near the urethra. The researches made upon the human embryo for the purpose have not sustained the conclusions of these two observers. Kolliker,4 Dohrn °and Rieder° found no trace of the Wolffian ducts in the lower portions of the vaginal canal.
According to Dohrn, at about the middle of pregnancy Gartner's canal reaches the uterine substance in the neighborhood of the spot which will later become the internal os. It penetrates the outer muscular layers of the uterus, and then descends forwards and inwards to the vaginal vault. In the fornix itself Gartner's canal lies in the concentric tissue layer which surrounds the Laquear vagina, underneath the mucosa. The canal dwindles as it proceeds downwards; and in not a single case could Dohrn follow it to the urethral orifice. But he noticed that traces of the duct extend further down upon the right than upon the left side, and he ex plains this as being due to the pressure of the rectum. Dohrn finds the cause of the early disappearance of these ducts in the lower portion of the vagina, in the rarification and stretching which the urethro-vaginal septum undergoes in embryonal growth; and Rieder upholds the same view.
The vagina is situated high up in the fcetus (Figs. land 3), in the new born child, and in early youth (Fig. 4); and it is much nearer the anterior pelvic wall than is the case in adults. This position is largely dependent upon the situation of the bladder, which in early years lies mostly above the true pelvis; it was formerly supposed to be the normal position of the organ in the mature woman. Recent sections have shown, in agreement with clinical observation, that, leaving out of account the change caused by a full rectum or bladder, the normal position of the vagina is unite a different one. Frankenhatiser' is right in his statement that when blad der and rectum are empty, the vagina is not in the pelvis at all, but lies among the soft parts of the pelvic outlet; and that its axis does not cor respond with that of the pelvis, but lies in the antero-posterior diameter of the pelvic outlet. (Fig. 5.) The length and breadth of the vagina vary considerably. According to Henle, the posterior wall is 2.8 inches long upon the average, while the anterior wall is 4 to f inch shorter. Its greatest width is at its upper portion near the fornix vaginEe; it is nar rowest at the entrance, where the hymen is situated. The walls of the vagina are applied together so as to form a square, transverse slit, about 1 inch in breadth; and so that a sagittal section will give one a linear ori fice. At various places we will, however, find upon minute examination that, owing to the columna rugarum, the transverse slit is irregular. Thus Henle makes the section -shaped. (Fig. 6.) In children and young people the square is relatively narrow.