c. Congenital ventral hernia. — The abdo minal cavity may also remain open, below the umbilical cord (Fried, Hasenest, Bouchard). This produces congenital ventral hernia. The viscera lie exposed, or are covered by the peritoneum.
d. Acquired umbilical hernia. —Hernia in the umbilical cicatrix ought to be distinguished from all these forms of ectopia. It is not a congenital deformity, but is produced after birth by an expansion of the umbilical cicatrix to a globular, a cylindrical, or a conical tumor. It is often observed in adults. If we adopt for these the name of acquired, and for those of new-born children that of congenital hernia, it would be better to give to the true con genital umbilical hernia the name of hernia funiculi umbilicalis (Seiler).
4. Fissure of the pubic and hypogastric Regions.
It sometimes happens that the pubic region alone remains open. For a correct idea of the malformations produced by it, it should be borne in mind that in the Mammalia, and, as re cent observations teach, also in Man (Bischoff, Wagner, A. Thompson, Coste, Sevres, Ar nold), the urinary bladder is formed by the allantois. This is originally in communication with the inferior part of the intestinal canal, so as to form for both a common outlet, called a cloaca, from which are evolved at a later period the peripheral openings of the in testinal tube, and of the uropoietic and ge nerative organs. The pubic bones are formed later than the iliac, (Meckel) and the pre viously existing ischiatic bones. Their forma tion proceeds from the outside to the inside ; therefore they are at first separated from each other by a large interval, and subsequently ap proach each other, in a gradual manner, for the formation of an amphiarthrosis. The fcetus may be arrested at this period of incomplete pubic articulation. In an observation of Walter, there was a fissure in the pubic region, though the genital and uropoietic organs were not malformed. This is the normal condition of some mammalia, and of the majority of birds. An arrest of deveopement may also take place at the period when there exists a fusion between the rectum and the allantois. Of this various forms occur.
a. Formation of a cloaca.— A cloaca is said to
exist, when the generative and urinary organs and the rectum have a common outlet. This is often complicated with ectopia of the tho racic and abdominal viscera. The cloaca may also exist alone. In its highest degree, the ureters, the imperfect organs of generation, and the opening of the rectum, are situated close to each other in a circular depression (Petit). In other cases, which approach more to the natural condition, there is a primordial urinary bladder, formed of two se parate parts (Merv), or merely constituted by its bare posterior wall. Fig. 602. shows how the fissured urinary bladder may be complicated with the formation of a cloaca.
In most of the cases which I have pub lished, the opening through which the are evacuated, is formed by the ileum, and the rectum is closed or wanting. This con firms the original formation of the intestinal tube by a mouth- and anus-gut. In a case men tioned by Jung these two portions are quite separate, and have each its separate open ing on the prolapsed posterior wall of the urinary bladder. When these two openings are fused, the cloaca persists, but approaches more to the natural condition. This may take place in different ways :— 1. The orifices of the ureters only may be found on the posterior wall of the bladder, or in the so-called in verted bladder, while the rectum still coheres with the genital organs, just as in the cases of imperforate anus just mentioned (Meckel, Burns), or with an open anus, as in the cases of Zhryham, Oliver, and Bonnet ; this condi tion approaches the nearest to the natural state, if the urinary bladder is complete (Martin); 2. The rectum may be separate, while the uri nary bladder remains fissured and fused with the genital organs (:Heckel, Gross); 3. The fissured urinary bladder may be separated from the anus, without taking up the ureters, which then open themselves into the rectum (Meckel, Oberteuffer). In some cases the outlets of these three apparatus are found not on a flat surface, but in a cavity. The cloaca, existing previously on the surface of the body, is then removed from it and folded in, so as to form a cavity.