The inguinal canal terminates in front at the external ring, which is formed by a separation of the fibres of the external oblique muscle as it passes inwards and downwards to be inserted into the pubis. Almost immediately after the muscle has become tendinous, a disposition to this separation is observable, and a kind of split is formed in the tendon, the edges of which are, however, pretty firmly held in their re lative positions by fibres passing closely and irregularly across from one to the other. These fibres have been called the intercolumnar fascia. Besides these there is a very remarkable ar rangement of tendinous fibres seeming to arise from Poupart's ligament, and thence radiating in an arched furor (the convexity of the arch looking towards the pubis) to form a strong in terlacement with the fibres of the external oblique.t Independent of these adventitious bands the tendon itself, as itapproaches the eru ral arch and the pubis, seems to become thicker and stronger ; and (as has been remarked by Scarpa) in the dead body after the integuments are removed and the parts left for some time exposed, the lower portion of the aponeurosis appears opaque and dense, while the part above the umbilicus preserves its transparency, and allows the fleshy fibres of the subjacent muscle to be seen through it. The separation above alluded to being effected, the tendon is divided into two portions, termed the pillars of the ring : the anterior or internal is broader and flatter, and runs to be inserted into the pubis of the opposite side, and the ligamentous sub stance that covers the front of this bone. The inferior or external is rounder and more firm, and attached to the external part of the crest or tuberosity of the pubis. A triangular aperture is thus formed of about an inch or an inch and a quarter in length, the base of which, nearly half an inch across, is situated at the pubis, from which it tapers gradually off in a direction upwards and outwards. For a neat deinonstra tion of this aperture we must also be largely indebted to the knife of the anatomist, its edges being obscured by a fascia' which comes off from them, and passing down on the cord is generally of sufficient density to admit of being traced as far as the tunica vaginalis testis. This ring is never well developed in the female, it then being smaller, rather of an oval figure, and from its deficiency of size appearing to be nearer the pubis than in the male : even in subjects of the latter sex the size of this open ing exhibits considerable variety. When a hernia has descended through it, the shape and direction of the external ring are altered : the inferior pillar is still more flattened and runs in a more horizontal direction ; the superior is banded in an arched form rather tightly above it ; the shape of the entire ring is rendered more oval and its direction more horizontal ; but still its relative position with respect to the bone is so far preserved that no hernia can pass, with out its internal edge resting on this bone.
In dissecting a hernia of this description from without, after removing the skin and cellular tissue more or less loaded with fat, the fascia superficialis is exposed. This is a tegu ment investing most parts of the body, though fir more dense in some situations than in others, and is situated beneath the subcuta neous fat, with which it is sometimes so much identified as to render its demonstration diffi cult. At the groin it is usually well developed, and is described as consisting of two distinct lamina', but may (by such as are curious in these dissections) by care be separated into many morel- The superficial layer is very lax, passes over and has no connexion with Poupart's ligament, and is very generally re moved along with the skin and fat by the in experienced dissector. Its removal exposes
some of the glands of the groin. The deep layer is more membranous, and possesses more of the determined character of a fascia. It adheres intimately to the muscular fibres of the external oblique, passes thence inwards over the tendon, to which it. cannot be said to be attached, as the connecting cellular tissue is extremely loose, and meets its fellow of the opposite side at the lines alba, to which both are attached. It has an insertion into the pubis, and its adhesion to Poupart's ligament is in many respects extremely intimate. Pass ing down in front of the thigh, it covers" several of the lymphatic glands, or in many instances leaves small apertures or deficiencies in which glands are lodged : it then reaches the opening in the fascia lata for the transmission of the saphena vein, to the edge of which it adheres more or less closely, and afterwards descends upon the thigh, having this vein interposed between it and the fascia lata. At the external abdominal ring the fascia superficialis sends down a sheath-like process, investing the cord and descending down over the timica vaginalis and the testicle : it must, therefore, under any circumstances give a covering to the hernial sac. On the removal of this, the fascia that comes from the edges of the pillars of the ring is observed, and this is generally much thicker and firmer than in the normal condition of the parts. When so thickened, it also admits of subdivision into several laminae. Immediately underneath is the cremaster muscle, its fibres spread out and separated so as to resemble a fascia, though in some instances the contrary may be observed, and they are seen gathered into bundles and greatly thickened. Still deeper are three other layers of fascia, perhaps derived from that which comes from the edges of the internal ring, and finally the hernial sac is exposed.
In bernim of moderate size, the spermatic artery, veins, and the vas deferens are usually found in one cord and enclosed in one common sheath lying behind the sac : some exceptions, however, to this rule are observed, one of which, wherein the bloodvessels are situated on its anterior and external surface, and the vas defe rens posteriorly and internally, has been already noticed and explained. But there is another deviation that seems to be occasioned by the growth of the hernia, and the compression exer cised by it on the cellular substance connecting the constituent parts of the cord together. It can therefore only be met with in large and old ruptures. Thus, as the tumour increases, it causes this cellular tissue to be stretched just as if the vas deferens and the artery were pulled asunder in different directions, whilst the sac insinuates itself between them, until finally the vessels come to lie on one side of the hernia, or it may be to occupy its anterior surface. The greatest divarication of these vessels exists, as might a priori be expected, towards the lower part of the tumour; it is less towards the middle, and scarcely if at all above, and in the vicinity of the neck of the sac. A knowledge of this fact may teach us to beware how we prolong an incision very far down in operating on large and old hernite.