The causes of this hernia are said to be three. fold an unnatural weakness of the conjoined tendon ; its absence altogether in consequence of malformation; and its being ruptured by direct violence. Of these, the second is not likely to occur, and an example of it had not been met with by Sir A. Cooper at the time of the publication of his work : the other two in effect amount nearly to the same thing, or at least stand towards each other in the relation of a predisposing to an immediately exciting cause.
The hernia by direct descent is distinguished from the oblique, 1st, by the appearance of the groin, the apex of the tumour being at the situation of the external ring, and there being no enlargement whatever in the direction of the inguinal canal : this diagnostic, however, has been found fallacious, for in old oblique hernia the internal ring is dragged down and made to approach the external so as to appear to form one continuous opening. Nor is it easy to point out the difference even in dissection ex cept by the position of the epigastrie artery, which in case of oblique descent always lies to the pubic side of the neck of the sac. The neck in some of these cases appears to be arched over and strongly constricted by the superior portion of the ruptured conjoined tendon, which in these cases is more than usually developed, and (as it were) in a state of hypertrophy. 1 t was probably this appearance that led to a belief that strangulation was occa sionally produced by the action of these mus cles. 2nd, By the relative position of the tumour with respect to the different structures composing the cord. The cremaster muscle in any hernia cannot be felt, but it occupies nearly its usual position in this, being spread out like a fascia in front of it, but rather towards its outside. The spermatic cord properly so called passes on its external rather than on its pos terior side ; and although all its constituent vessels may be separated in this as in any other species of large and old hernia, yet generally there is less divarication in this, and the parts lie together more compactly. 3rd, " This
tumour differs from the common bubonocele in being situated nearer the penis."* This is cer tainly true when it is only bubonocele; but when it has descended into the scrotum, the same difficulty that has been noticed as apper taining to old ruptures must also obtain here. In applying this diagnostic the student must recollect that the internal edges of both hernia are equally near to the pubis : it is by looking to the external border of the neck of the tumour that he can render the test available. Scarpat states that this hernia is returned without being attended by the gurgling sound : this, however, is an observation perfectly new to me, and which I can by no means verify. Lastly, these hernia appear more suddenly and attain a larger size more rapidly: frequently theyappear as scrotal ruptures almost from the earliest period. This, however, is still an uncertain criterion, and in deed with the assistance of all these circum stances it is always so difficult and frequently so utterly impossible to establish a diagnosis, that no operation should be undertaken under the conviction of the disease being certainly of one form or of the other.
This rupture should present to the anatomist the same number of layers of fascia as that by the oblique descent, the fascia transversalis sup.. plying the place of that given off from the edges of the internal ring; / but the young surgeon should be cautioned not to expect the same facilities of demonstration in the living subject that he possesses in the dead. In the former, the operator often meets with layer after layer of fascia, numerous beyond his expectation, and to which he can give no name; and it is no un common circumstance for him to operate on and return a rupture without being able to say of what nature it was—nay, even as to its being inguinal or crural.