83, may be found a well-marked case of duplicity of the urinary bladder described by Zuinger, whose account is accompanied by a plate, which perfectly confirms the description ; but this case occurred in an ox.
within the cavity of the bladder, more or less perfect septa are found, by which that organ is divided into two or more compartments. This condition is met with or occurs under two very different circum stances : in one it is a congenital affection, and this it is our business to consider in this section ; in the other it is produced by and is not an uncommon consequence of retention of urine during extra-uterine life. In the de scription of these two very dissimilar affections much confusion has occurred, in consequence of an almost universal impression that they were similar the one to the other. If the theory of the eccentric development of organs, proposed by Geoffroy St. Hilaire, and extended by M. Serres, be admitted, all difficulty in explaining this seemingly singular congenital phenomenon vanishes. M. Serres conceives that he has triumphantly established the fact, that the hollow organs, which are single and placed on the median line, are composed of two moieties, primitively distinct and sepa rate ; so that according to him, at a certain period of uterine life, there exist two aortas, two basilar arteries, two superior caves, and so on. Now if there exist two vaginae, two bladders, two uteri, at a certain epoch of embryotic life, the evolution of these organs should necessarily present three successive periods : a first, characterised by their du plicity and their complete isolation; a second, by their mutual approach and union upon the median line ; a third, by their complete fusion, which constitutes their permanent condition in man and the mammalia. We can therefore conceive that at the moment of the second period, when the two primitive organs are united, the parietes of both being entire and in contact on the median line, there will be a perfect septum separating the one organ from the other. At the commencement of the third period in the process of develop ment, the septum is destined to disappear, the two cavities merge into one, and the work of development in the organ is com plete. Now, in the evolution of all the organs, development may be arrested at any period of its progress : it may be arrested before the organs come into contact, in which case there would be two bladders; it may be arrested after they have formed a junction, in which case a complete septum would exist, as in the case described by Blasius ; or the check may not occur until a greater or less portion of the septum shall have disappeared.
To distinguish the congenital affection which is a consequence of arrested development, from the acquired affection which is an extra uterine disease, and is commonly an effect of retention of urine, is not difficult. In the
former we shall always find that the entire of each pouch is invested by a layer of mus cular fibres ; in the latter, it will be found that in one of the two compartments no such mus cular investment is present.
Extrophy or extroversion.—Extrophy of the bladder was, up to a comparatively late period, almost universally regarded as a hernia of that organ; and it was not until about the middle of the last century, and after Tenon had dissected two such cases, that this opinion was shown to be erroneous.* Tenon dis covered that there was a complete " absence" or destruction of the whole of the anterior parietes of the bladder; and that the tumour which is found at the hypogastrium is only the posterior parietes of this sac, with the " trigone " pushed forward by the abdominal viscera, as if for the purpose of blocking up the opening caused by the deficiency of sub stance below the umbilicus. On the surface of the tumour which is there presented, and at its inferior part, we see the urine almost con tinually exuding through two holes, pierced in the centre of two small nipple-like eminences, which are the orifices of the ureters. The insertion of these conduits of the urine at the inferior part of the tumour indicates that the portion of the bladder, which appears upon the exterior, is precisely that which, in the natural state, is found most deeply situated in the pelvic cavity, the internal surface of the posterior and inferior portion of the organ. The researches of anatomists have most posi tively confirmed these indications, by shewing that in extroversion of the bladder the anterior part of this organ is more or less completely wanting, and that the posterior part is pushed from behind forwards, through the large open ing which results from this absence, causing a " hernia," either between the two pubes and the two recti muscles, or, which is very rare, only between the latter, the mucous mem brane being presented externally. By this displacement the external posterior surface of the bladder forms a concavity in which some portions of the intestinal tube may be impacted, as in a true herniary sac, especially when the abdominal muscles and the diaphragm are strongly contracted. The volume of the tu mour is on this account variable, not only as between one subject and another, but in the same subject at different ages. Thus in new born infants only a slight projection is presented: the tumour may not occupy a larger space than from half an inch to an inch. In adults it may project to the extent of two or more inches and present a transverse diameter of four or five. The tumour is then smooth and frequently appears divided into two lobes.