The superior wall of the abdomen sometimes presents a defect of development, giving rise to the congenital perforation of the diaphragm, through which hernim take place into the thorax. Such a perforation may exist on either side, although it is much rnore frequently found upon the left. (See DIAPHRAGM.) The malformation commonly known under the name of extroversion of the bladder,' has also connected with it an imperfect state of the anterior abdominal wall inferiorly, in conse quence of the separation of the ossa pubis and of the recti abdominis muscles, and I be lieve, in general, the absence of the pyrami dales. (See BLADDER, ABNORMAL ANATOMY.) In these cases the umbilicus is generally situ ated much lower than usual, and some writers have fallen into the absurd error of supposing that it was absent altogether, in consequence of its having escaped their notice by being covered and concealed by the protruded blad der.
A second class of congenital malformations of the abdominal parietes arises from an excess in the development of certain parts, as a nu merical increase in the muscles, vessels, or nerves entering into the formation of the abdo minal parietes, or from the development of a part of' a second fcetus in connexion with the abdomen. Of the former it is extremely rare to meet with instances among the muscles or vessels of the abdomen ; occasionally we do find an unimportant increase in the number of the costal attachments of one or more of the muscles. As to the latter several cases are recorded in which fcetuses exhibited an arm or leg, or even a portion of the trunk of another implanted upon the abdominal wall, or, as is a very rare occurrence, included in it; con stituting a subdivision of that form of mon strosity which has been called Diplogenesis. We refer to the article MONSTROSITY for details on this subject.
Morbid conditions of the abdominal parietes. —These are such as are common to all parts compounded of the same elements as enter into the formation of the abdominal walls, which it would be superfluous to particularise here.
Congenital malformations of the abdominal cavity.—In many acephalous fcetuses the ab dominal cavity is more or less curtailed of its due proportions, the deficiency existing at its snperior part. Where the inferior part of the thorax or the pelvis is malformed, the abdo minal cavity will also be necessarily more or less affected.
Under this head we may refer to the ano malies which arise from the congenital mal position of the viscera, which may extend to the whole contents of the abdomen, or may affect only one or more viscera. Such are the cases of complete transposition of the viscera, where those which in the normal state are on the right side are found upon the left, and vice verscl; thus the liver is found on the left, the pylorus on the left, the cardiac extremity of the sto mach and the spleen on the right, &c. &c. The aorta and vena cava too change places, and the openings in the diaphragm alter their po sitions along with the parts which respectively pass through them. The same transposition generally extends also to the thoracic viscera. In many of the instances in which this trans position has been observed, the individuals have lived to the adult period of life without ex hibiting any symptom indicative of the unusual position of the internal organs.* Single viscera are likewise often found trans posed or in unusual positions, occasioning necessarily corresponding changes in the parts which are connected with them. It is unne cessary to allude further to them here, as they will be treated of in the articles appropriated to those viscera.
The morbid conditions of the abdominal cavity are the results of disease affecting its lining membrane or its contained viscera and other parts intimately connected with it. See PERITONEUM and INTESTINAL CANAL.