ACQUIRED CHANGES.
Sacculi or cysts.---A sacculated or encysted condition of the bladder is never a congenital vice of conformation of that organ, but an effect of disease. Sacculi may be produced by any thing which can oppose itself to the excretion of urine, or which may enfeeble the muscular tunic of the organ. In this way the urine becomes collected in the bladder, the parietes are distended, the internal tunic is forcibly applied upon the muscular coat, and if at any point this tunic be weakened, less resistance is offered, a separation between some of its fasciculi takes place to a sufficient dis tance to admit of the mucous membrane pass ing between them, and in this way sacculi may be formed.
This, however, is not the only way by which this state may be produced ; in some bladders the muscular tunic is so developed, probably by irritation, that its fasciculi are grouped and a columnar aspect is produced, not very unlike to the appearance of the interior of the ven tricles of the heart.
Certain portions of the parietes of the organ are in such cases unprovided with the muscular fibre necessary to enable them to oiler the usual resistance, and a similar effect is pro duced to that which I have already described, the mechanism being somewhat different.
These sacs may attain great size, even supe rior to that of the bladder itself; commonly the point by which communication with the bladder is maintained is only a narrow neck, and in consequence of this circumstance the organ has occasionally been described as dou ble, triple, and so on. It is always easy to determine whether it be really so or not, first, by examining the parietes of each, and, secondly, by ascertaining the points at which the ureters are implanted. In the first case we shall find only one of these compartments invested by a muscular tunic : in the second an ureter has never yet been known to pene trate directly the adventitious cavity.
There is scarcely any point of the surface of the bladder in which such a state may not be produced, but there are certain regions where the affection is much more frequently met with than others. They are most commonly formed at the lateral parts, or at the summit, near the insertion of the urachus. Occasionally many of these sacculi are found in the same bladder." A species of sacculi or appendices may, however, be produced by an extension, at a given point, of the whole of the vesical tunics ; and evenikthese may be a consequence of re tention of urine, but more frequently of the sojourn of a stone, which forms a cell. Some examples of this species are given by Morgagni.t A woman, two years before her
death, introduced into the urethra " a long hair pin ;" this instrument slipped from her grasp and passed into the bladder, where it became arranged transversely, so that whilst the point rested upon the left, its head rested on the right side of the organ. The head became incrusted with calcareous matter; a stone of the size of a nut was thus formed, which was contained in a quadrilateral sac produced by the extension of the whole of the tunics of the bladder.
Cells or cysts may be otherwise formed at the expense of the vesical parietes. Calculous concretions may be formed in the kidney, and may pass unobstructed through the ureter into the bladder; but if the magnitude of the stone be disproportioned to the capacity of the canal of the ureter, it may sojourn at any point of the continuity of this canal, or at the point where it terminates in the bladder. If also the cal culous matter be abundant in the urine, it will be deposited upon this nucleus, which will more or less rapidly augment in volume, and will be impacted at or near the point where it may have acquired this augmentation. The first author who speaks in a clear and precise man lier of this affection is the celebrated Pierre Franco.'" Since Franco, it has been described by by many others, particularly by Alexander Mon rot and Iloustet4 The existence of this affection is certainly not frequent,but its occasional occur rence is amply proved : formed in the way I have described, these calculi occasionally glide between the mucous and muscular tunics of the organ by means of an opening which they form at the point where the ureter obliquely pierces the bladder, instead of entering the bladder by the natural channel. The volume of these cysts is never very considerable, for such calculi do not acquire anything like the volume of those which are commonly found moving freely in the cavity of the bladder. The reason of this is ob vious; they are not exposed to the action of any considerable quantity of urine, and they cannot consequently receive a large accession of calcu lous matter. Covillard§ and Garengeot II have seen them of the size of a hen's egg, but such cases are rare. Commonly they are very little removed from the insertion of the ureters. The reason of this is not, however, that which was assumed by because the contraction of the muscular fibres is made towards the fundus, and that in consequence the calculus would be forced towards that region, but by reason of the resistance offered by the membrane of the cyst by which they are surrounded.