In persons more advanced in life in whom the opening in the tendon had been perfectly closed, Scarpa denies that it ever becomes relaxed again, and therefore states that the rup tures which occur from over-distension, from pregnancy, or as the sequelm of dropsy, are not situated in the original umbilical canal, but in some part of the linea alba that has more recently given way, and of which the umbilicus happens to form a part. l le states fluffier that the linea alba is not equally strong and firm in all its parts ; that above the navel it becomes gradually thinner, and in women who have borne many children it is uneven in consistence, and in some parts so weak as to be liable to yield and tear on a very slight exertion. Bence it happens that these ventro-umbilical ruptures generally occur rather above the navel ; and the almost obliterated remains of this cicatrix (fur by the distension it becomes nearly smooth) is scarcely ever observed to occupy the centre of the tumour, but is found to one side and almost placed inferiorly. In the dissection of these tumours a laceration or fissure is constantly met with in the linea alba, sometimes transverse, but more generally longitudinal, and this is one reason why the umbilical ruptures of old per sons are not susceptible of a radical cure, fur there is a great difference between a natural opening, the tendency of which is to contract and close, and one made by the yielding and laceration of part of the linea alba or other tendinous portion of the abdominal parietes, which certainly cannot be supposed to be en dowed with strong reparative properties.
There was a question formerly raised as to whether umbilical hernia possessed a peritoneal sac, and it was generally believed that no such investment had any existence in the disease. Garengeot in his paper on singular species of hernim expressly states that ruptures of this kind were deficient in this particular, and he was followed by Petit and almost all the elders of our profession, who, to spare themselves the labour of investigation, copied from each other errors as well as truth. It is really curious to observe how a mistake could have so long maintained its ground that could have been set at rest by half—an-hour's dissection ; and indeed it is in some respects surprising how such an opinion came to be entertained at all. In every case of umbilical hernia there must of neces sity be a sac, because the peritoneum is not deficient at the navel, and the vessels that pass within the cord do not enter the cavity they lie anterior to it, and are partly invested by the membrane, which is entire and complete behind the navel, and neither intestine nor omentum can be protruded without pushing it out before it, and thus constituting a proper hernial sae. It may be that in large umbilical hernia the peri toneum shall have become very thin, so that the peristaltic motions of the intestines may be easily perceived through it from without ; or it may have been burst accidentally, and in either of these cases there will be an appearance as if there had been in reality no sac. And more
over, the peritoneum immediately behind the navel is not connected to it by the same loose and distensible cellular tissue that unites it to other parts : it is here very closely joined, and consequently in small ruptures only occupying this spot there will be no appearance of a sepa rate and distinct sac, although the peritoneal covering is really there notwithstanding. It must be borne in mind, however, that invest ments of umbilical ruptures are always very thin, and a proportionate degree of caution is requisite in cutting through diem during ope ration. There arc no distinct layers of fascia here as in other ruptures, no laminae. to sepa rate one by one and one after another. In the congenital species the contents of the sac are merely covered by the peritoneum and the sheath of the cord. In the infantile, the coverings are the skin and cicatrix of the navel and the peritoneum ; and in the adventitious kind or ventro-mnbilical we meet the skin, then the superficial fascia, which is very thin and weak on this part of the abdomen ; next the cellular tissue that had united the peritoneum to the adjacent structures, and which may have become condensed so as to form a kind of fascia propria ; and lastly, the peritoneum or hernial sac itself.
In almost every case of umbilical hernia occurring in the adult, omentum has formed part of the contents of the sac, at least the ob servation has been so universally made that the rule may be considered as established. In general it lies before the intestine in such a po sition as to conceal it altogether and make it appear as if no other viseus was engaged ; but sometimes the intestine makes a passage through it and presents first when the sac is opened ; or both these structures may be coiled and twisted together in such wise as to render it difficult to unravel and separate them one from another, and highly perilous to return them in that con dition into the cavity lest strangulation should take place within. From the circumstance also of containing omentum, umbilical ruptures frequently become irreducible, this structure, when protruded, becoming thickened and en larged and occasionally loaded with fat, so as to preclude the possibility of its being again returned through the tendinous opening. Or adhesions may have formed between the omentum and the intestine, or between either or both of these and the sac : in short, the rupture may become irreducible from any of the causes already mentioned as capable of producing such a condition of parts, but the one first alluded to, namely, the thickening and alteration of the omentum, is the one most generally observed.