The so-called double hymens are hence nothing more than partial median adhesion of the young epidermic cells. It is unnecessary to refer to the number of reported cases of atresia hymenalis, especially since Breisky has dwelt upon the subject at sufficient length.
Anus Vaginalis and Vestibularis.—We have already stated our opin ion that complete absence of the external genitals, associated with normal development of the internal, had never to our knowledge been met with. Where the external genitals form, the genital furrow is always present. The anomalies in development result only from the fact that the canals formed from the genital furrow either do not differentiate correctly, or else that the vaginal walls do not develop sufficiently downwards. When one of the three canals of which we are speaking does not reach the geni tal furrow, it must end blind. Where the intestinal canal, for example, does not open freely externally, the child suffers from atresia ani.
It may happen now either that the anal opening, as we will for the present call the lower end of the genital furrow, lies near to the blind end of the intestinal canal, so that only a thin wall is to be overcome, or else the end of the intestinal canal opens into the uro-genital sinus, into the vagina, or into the bladder.
In other instances, where broad tissue layers intervene between the anal crease or anal opening, and the blind intestine, we cannot say that the two organs are undeveloped, but, on the contrary, when a trace of anal opening or of anal crease is present, we are only able to eay that the end of the intestine did not reach the anal depression When the extremity of the intestinal canal opens in the uro-genital sinus, in the vagina or in the bladder, we are dealing with defective de velopment of the vaginal walls separating the canals.
Such defective development of one or of another vaginal wall is a rem nant from the period of embryonic life. It is to be borne in mind that the allantois is a diverticulum from the embryonic rectum, and that from the outset communication exists between the two organs, embryonic rec tum and bladder (allantois). Such is the condition up to the fifth week of fcetal life. Normally the rectum and the bladder then become sepa rated. In the female, Miiller's ducts spread between, so that in little girls opening of the rectum into the bladder is of very infrequent occurrence. If now the septum between the intestine and the bladder forms only in completely below, then will the site of communication lie deeper, and yet the anus not be in its normal place. There results in the female an open ing into the vagina, an anus vaginalis, and lower down an anus vulvaris or vestibularis, better termed anus uro-genitalis since the opening takes place into this sinus. Further still there occurs in the same sex an anus
perinealis, where the anal opening is at the posterior cornmissure. In a reported case there was present between the posterior commissure and the anus an opening connected with a pouch three-quarters of an inch deep, which communicated above with the rectum. Defzecation occurred at times by the anus and then again by this opening in the perineum.
In case of all varieties of abnormal opening of the rectum, it is of prime importance to the individual, as to whether there exists a sphincter muscle or not. Biwisch reports a ease where a woman of twenty-six, affected with an anus vaginalis, was able to retain faxes, while, in con trast, a little girl of two had no retentive power whatsoever.
Since fissures of the abdominal wall have an influence on the external genitals, we must briefly discuss them here. The abdominal walls close concentrically t. the umbilicus, by approaching one another laterally, and from above below, owing to incurvation of the embryo on its longitudinal axis. When traction exists at the umbilicus, the intestines are drawn out of the abdominal cavity, and closure of the abdominal wall becomes impossible. Opinions vary as to whether such traction is exerted on the omphalo-enteric duct, or on the urachus. The first view was originally ' advocated by Bartels and by Ahlfeld, as the result of many personal ob servations. On the other hand, Ruge and Fleischer claim that the causal factor is traction on the urachus. The important factor is lengthening of the urachus outwardly. We believe that both traction exerted on the omphalo-enteric duct and on the urachus are causal factors. The effect of outward lengthening is that closure of the abdominal walls downwards is prevented, as also union of the parts which lie in front of the allantois. A further cause is overfilling of the allantois and its displacement. The one is the natural sequence of the other, but the cause of the over-disten sion is purely hypothetical. It is possible that the starting-point lies in the lessened capability of distension of the prolapsed allantois, and that on this account the urinary cloacae, that is to say, the cloacae of the genital furrow, do not increase sufficiently in size, on account of the lessened pressure. There then results lack of development of the cloacae, since the composite portions do not reach one another, and emptying of the intestinal and bladder contents cannot take place. Overfilling and pro lapse of the allantois are the necessary consequences.