CRURAL OR FEMORAL HERNIA takes place at the superior and internal part of the thigh, below the fold of the groin ; the intestine pass ing out of the abdomen behind Poupart's liga ment, between it and the transverse ramus of the pubis, through an aperture that has been termed the crural or femoral ring. A know ledge of the constitution, size, and boundaries of this ring most be of the last importance to the practical surgeon, and accordingly no part of the body has been examined with more minute attention ; yet if by these labours ana tomy has gained in accuracy of information and very diffuse description, still the student is not much the better for it, inasmuch as almost every anatomist has adopted views peculiar to himself, and thus in the details a degree of con fusion has been produced that is extremely em barrassing to the beginner. I shall, therefore, avail myself as little as possible of authorities, and endeavour to describe these parts as they appear upon dissection, commencing from within, which is perhaps the best mode of studying the anatomy of every species of hernia.
The distance between the anterior superior spinous process of the ileum and the angle of the crest of the pubis is in the well-formed female about five and a half inches in length, along which space Poupart's ligament is stretched like a bow-string from point to point. The distance from the ligament thus extended, backwards to the edges of the ileum and pubis forming the border of the pelvis, varies accord ing to the elevations and depressions of these bones ; but the entire forms a very considerable space, which is, however, in general so well filled up that unless under peculiar circum stances this region affords sufficient support and protection to the viscera of the abdomen. On examining the corresponding peritoneal sur face within, the membrane is found capable of being detruderl only at one spot, internal to the view, and about an inch and a half distant from the symphysis pubis. here, there is a natural aperture varying in size in different subjects, into which the finger may be pushed by a little violence, and a small artificial hernial sac like a thimble be thus produced. On tearing off the peritoneum it is easy to observe the dif ferent arrangements that serve to support and strengthen this region of the abdomen.
From Poupart's ligament three distinct layers of fascia pass off in different directions. The fascia transversalis has been already described as passing upwards on the front of the abdomen, where it is gradually lost. From the inferior and posterior part of the arch another fascia passes, at first downwards, then upwards and backwards, to expand itself over the iliacus interims and psoas muscles ; and it is therefore called the fascia iliaca. These fascia: are per fectly continuous as far inwards as the external border of the artery, and form a smooth and swan membranous wall for the abdomen in this situation, rather attached to Poupart's liga ment than coming off or derived from it.* These fascia: separate at this spot and unite again between the artery and vein, thus forming a sheath for the former vessel : in like manner a separate sheath is formed for the vein, when they again separate and leave a small opening, which is the crural ring, but unite before they reach Gimbernat's ligament, to the abdominal surface of which they give an investment, but here the fibrous structure is very weak and differs little in appearance from cellular mem brane. These fascias then form a flat, broad funnel, which has three apertures at top, and the membranous septa are of the greatest use in binding the anterior and posterior faces of this funnel together : hence a hernia cannot escape through in company with the artery nor with the vein, and hence also the vein is not com pressed nor its circulation interfered with, even although a hernia close to it is in a state of strangulation. This funnel descends on the vessels, to which it becomes firmly attached, at about an inch and a half below Poupart's liga ment, and, according to some anatomists, is there reflected up again on the vessels forming a cul-de-sac or bag. I thus consider the crural ring properly so called to be an aperture formed by a deficiency in the fascia iliaca and transversalis, just as the internal inguinal ring is formed in the latter membrane alone. It is occupied by a loose cellular tissue, and in general by a small absorbent gland.