Surgical Anatomy Part 26

W. The lower part of the iliacus muscle.

[Ill.u.s.tration: Abdomen and leg, showing blood vessels, muscles and other internal organs.]

PLATE 30

PLATE 31.

A. The anterior superior iliac spine.

B. The umbilicus.

C. The spine of the pubis.

D. The external oblique muscle; d, its tendon; d*, the external ring.

E. The internal oblique muscle.

F. The transverse muscle; f, its tendon; forming, with e, the conjoined tendon.

G. The rectus muscle laid bare.

H h. The fascia spermatica interna laid open above and below d*, the external ring.

I. The peritonaeum closing the internal ring.

K. The fascia transversalis; k, its pubic part.

L. The epigastric artery and veins.

M. The spermatic artery, veins, and vas deferens bending round the epigastric artery at the internal ring; m, the same vessels below the external ring.

N. The femoral artery; n, its profunda branch.

O. The femoral vein, joined by--

P. The saphena vein.

Q. The sartorius muscle.

R. The sheath of the femoral vessels.

S S. The falciform margin of the saphenous opening,

T. The anterior crural nerve.

U. The pubic part of the fascia lata.

V. The iliac part of the fascia lata.

W. The lower part of the iliacus muscle.

[Ill.u.s.tration: Abdomen and leg, showing blood vessels, muscles and other internal organs.]

Plate 31

COMMENTARY ON PLATES 32, 33, & 34.

THE DISSECTION OF THE OBLIQUE OR EXTERNAL AND THE DIRECT OR INTERNAL INGUINAL HERNIAE.

The order in which the herniary bowel takes its investments from the eight layers of the inguinal region, is precisely the reverse of that order in which these layers present in the dissection from before backwards. The innermost layer of the inguinal region is the peritonaeum, and from this membrane the intestine, when about to protrude, derives its first covering. This covering const.i.tutes the hernial sac. Almost all varieties of inguinal herniae are said to be enveloped in a sac, or elongation of the peritonaeum. This is accounted as the general rule. The exceptions to the rule are mentioned as occurring in the following modes: 1st, the caec.u.m and sigmoid flexure of the colon, which are devoid of mesenteries, and only partially covered by the peritonaeum, may slip down behind this membrane, and become hernial; 2nd, the inguinal part of the peritonaeum may suffer rupture, and allow the intestine to protrude through the opening. When a hernia occurs under either of these circ.u.mstances, it will be found deprived of a sac.

All the blood vessels and nerves of the abdomen lie external to the peritonaeum. Those vessels which traverse the abdomen on their way to the external organs course outside the peritonaeum; and at the places where they enter the abdominal parietes, the membrane is reflected from them. This disposition of the peritonaeum in respect to the spermatic and iliac vessels is exhibited in Plate 32.

The part of the peritonaeum which lines the inguinal parietes does not (in the normal state of the adult body) exhibit any aperture corresponding to that named the internal ring. The membrane is in this place, as elsewhere, continuous throughout, being extended over the ring, as also over other localities, where subjacent structures may be in part wanting. It is in these places, where the membrane happens to be unsupported, that herniae are most liable to occur. And it must be added, that the natural form of the internal surface of the groin is such as to guide the viscera under pressure directly against those parts which are the weakest.

The inner surface of the groin is divided into two pouches or fossae, by an intervening crescentic fold of the peritonaeum, which corresponds with the situation of the epigastric vessels. This fold is formed by the epigastric vessels and the umbilical ligament, which, being tenser and shorter than the peritonaeum, thereby cause this membrane to project.

The outer fossa represents a triangular s.p.a.ce, the apex of which is below, at P; the base being formed by the fibres of the transverse muscle above; the inner side by the epigastric artery; and the outer side by Poupart's ligament. The apex of this inverted triangle is opposite the internal ring. The inner fossa is bounded by the epigastric artery externally; by the margin of the rectus muscle internally; and by the os pubis and inner end of Poupart's ligament inferiorly. The inner fossa is opposite the external abdominal ring, and is known as the triangle of Hesselbach.

The two peritonaeal fossae being named external and internal, in reference to the situation of the epigastric vessels, we find that the two varieties of inguinal herniae which occur in these fossae are named external and internal also, in reference to the same part.

The external inguinal hernia, so called from its commencing in the outer peritonaeal fossa, on the outer side of the epigastric artery, takes a covering from the peritonaeum of this place, and pushes forward into the internal abdominal ring at the point marked P, Plate 32. In this place, the incipient hernia or bubonocele, covered by its sac, lies on the forepart of the spermatic vessels, and becomes invested by those same coverings which const.i.tute the inguinal ca.n.a.l, through which these vessels pa.s.s. In this stage of the hernia, its situation in respect to the epigastric artery is truly external, and in respect to the spermatic vessels, anterior, while the protruded intestine itself is separated from actual contact with either of these vessels by its proper sac. The bubonocele, projecting through the internal ring at the situation marked F, (Plate 33,) midway between A, the anterior iliac spine, and I, the pubic spine, continues to increase in size; but as its further progress from behind directly forwards becomes arrested by the tense resisting aponeurosis of the external oblique muscle, h, it changes its course obliquely inwards along the ca.n.a.l, traversing this ca.n.a.l with the spermatic vessels, which still lie behind it, and, lastly, makes its exit at the external ring, H. The obliquity of this course, pursued by the hernia, from the internal to the external ring, has gained for it the name of oblique hernia. In this stage of the hernial protrusion, the only part of it which may be truly named external is the neck of its sac, F, for the elongated body, G, of the hernia lies now actually in front of the epigastric artery, P, and this vessel is separated from the anterior wall of the ca.n.a.l, H h, by an interval equal to the bulk of the hernia. While the hernia occupies the ca.n.a.l, F H, without projecting through the external ring, H, it is named "incomplete." When it has pa.s.sed the external ring, H, so as to form a tumour of the size and in the situation of f g, it is named "complete." When, lastly, the hernia has extended itself so far as to occupy the whole length of the cord, and reach the s.c.r.o.t.u.m, it is termed "scrotal hernia." These names, it will be seen, are given only to characterise the several stages of the one kind of hernia--viz., that which commences to form at a situation external to the epigastric artery, and, after following the course of the spermatic vessels through the inguinal ca.n.a.l, at length terminates in the s.c.r.o.t.u.m.

The external inguinal hernia having entered the ca.n.a.l, P, (Plate 32,) at a situation immediately in front of the spermatic vessels, continues, in the several stages of its descent, to hold the same relation to these vessels through the whole length of the ca.n.a.l, even as far as the t.e.s.t.i.c.l.e in the s.c.r.o.t.u.m. This hernia, however, when of long standing and large size, is known to separate the spermatic vessels from each other in such a way, that some are found to lie on its fore part--others to its outer side. However great may be the size of this hernia, even when it becomes scrotal, still the t.e.s.t.i.c.l.e is invariably found below it.

This fact is accounted for by the circ.u.mstance, that the lower end of the spermatic envelopes is attached so firmly to the coats of the t.e.s.t.i.c.l.e as to prevent the hernia from either distending and elongating them to a level below this organ, or from entering the cavity of the tunica v.a.g.i.n.alis.

The external form of inguinal hernia is, comparatively speaking, but rarely seen in the female. When it does occur in this s.e.x, its position, investments, and course through the inguinal ca.n.a.l, where it accompanies the round ligament of the uterus, are the same as in the male. When the hernia escapes through the external abdominal ring of the female groin, it is found to lodge in the labium pudendi. In the male body, the t.e.s.t.i.c.l.e and spermatic cord, which have carried before them investments derived from all the layers of the inguinal region, have, as it were, already marked out the track to be followed by the hernia, and prepared for it its several coverings. The muscular parietes of the male inguinal region, from which the loose cremaster muscle has been derived, have by this circ.u.mstance become weakened, and hence the more frequent occurrence of external inguinal hernia in the male. But in the female, where no such process has taken place, and where a cremaster does not exist at the expense of the internal oblique and transverse muscles, the inguinal parietes remain more compact, and are less liable to suffer distention in the course of the uterine ligament.

The internal inguinal hernia takes its peritonaeal covering (the sac) from the inner fossa, Q R, Plate 32, internal to the epigastric artery, and forces directly forwards through the external abdominal ring, carrying investments from each of such structures as it meets with in this locality of the groin. As the external ring, H, Plate 34, is opposite the inner peritonaeal fossa, Q R, Plate 32, this hernia, which protrudes thus immediately from behind forwards, is also named direct.

In this way these two varieties of hernia, (the external, Plate 33, and the internal, Plate 34,) though commencing in different situations, P and R, Plate 32, within the abdomen, arrive at the same place--viz., the external ring, H, Plates 33 and 34. The coverings of the internal hernia, Plate 34, though not derived exactly from the same locality as those which invest the cord and the external variety, are, nevertheless, but different parts of the same structures; these are, 1st, the peritonaeum, G, which forms its sac; 2nd, the pubic part of the fascia transversalis; 3rd, the conjoined tendon itself, or (according as the hernia may occur further from the mesial line) the cremaster, which, in common with the internal oblique and transverse muscles, terminates in this tendon; 4th, the external spermatic fascia, derived from the margins of the external ring; 5th, the superficial fascia and integuments.

The coverings of the internal inguinal hernia are (as to number) variously described by authors. Thus with respect to the conjoined tendon, the hernia is said, in some instances, to take an investment of this structure; in others, to pa.s.s through a cleft in its fibres; in others, to escape by its outer margin. Again, the cremaster muscle is stated by some to cover this hernia; by others, to be rarely met with, as forming one of its coverings; and by others, never. Lastly, it is doubted by some whether this hernia is even covered by a protrusion of the fascia transversalis in all instances. [Footnote]

[Footnote: Mr. Lawrence (Treatise on Ruptures) remarks, "How often it may be invested by a protrusion of the fascia transversalis, I cannot hitherto determine." Mr. Stanley has presented to St. Bartholomew's Hospital several specimens of this hernia invested by the fascia.

Hesselbach speaks of the fascia as being always present. Cloquet mentions it as being present always, except in such cases as where, by being ruptured, the sac protrudes through it. Langenbeck states that the fascia is constantly protruded as a covering to this hernia: "Quia hernia inguinalis interna non in ca.n.a.lis abdominalis aperturam internam transit, tunicam v.a.g.i.n.alem communem intrare nequit; parietem autem ca.n.a.lis abdominalis internum aponeurotic.u.m, in quo fovea inguinalis interna, et qui ex adverso annulo abdominali est, ante se per annulum trudit." (Comment, ad ill.u.s.t. Herniarum, &c.) Perhaps the readiest and surest explanation which can be given to these differences of opinion may be had from the following remark:--"Culter enim semper has partes extricat, quae involucro adeo inhaerent, ut pro lubitu musculum (membranam) efformare queas unde magnam illam inter anatomicos discrepantiam ortam conjicio." (Camper. Icones Herniarum.)]

The variety in the number of investments of the internal inguinal hernia (especially as regards the presence or absence of the conjoined tendon and cremaster) appears to me to be dependent, 1st, upon the position whereat this hernia occurs; 2nd, upon the state of the parts through which it pa.s.ses; and 3rd, upon the manner in which the dissection happens to be conducted.

The precise relations which the internal hernia holds in respect to the epigastric and spermatic vessels are also mainly dependent (as in the external variety) upon the situation where it traverses the groin. The epigastric artery courses outside the neck of its sac, sometimes in close connexion with this part--at other times, at some distance from it, according as the neck may happen to be wide and near the vessel, or narrow, and removed from it nearer to the median line. At the external ring, H, (Plate 34,) the sac of this hernia, g, protrudes on the inner side of the spermatic vessels, f; and the size of the hernia distending the ring, removes these vessels at a considerable interval from, I, the crista pubis. At the ring, H, (Plate 34,) the investments, g f, of the direct hernia are not always distinct from those of the oblique hernia, g f, (Plate 33); for whilst in both varieties the intestine and the spermatic vessels are separated from actual contact by the sac, yet it is true that the direct hernia, as well as the oblique, may occupy the inguinal ca.n.a.l. It is in relation to the epigastric artery alone that the direct hernia differs essentially from the oblique variety; for I find that both may be enclosed in the same structures as invest the spermatic vessels.

The external ring of the male groin is larger than that of the female; and this circ.u.mstance, with others of a like nature, may account for the fact, that the female is very rarely the subject of the direct hernia.

In the male, the direct hernia is found to occur much less frequently than the oblique, and this we might, a priori, expect, from the anatomical disposition of the parts. But it is true, nevertheless, that the part where the direct hernia occurs is not defended so completely in some male bodies as it is in others. The conjoined tendon, which is described as shielding the external ring, is in some cases very weak, and in others so narrow, as to offer but little support to this part of the groin.

DESCRIPTION OF THE FIGURES OF PLATES 32, 33, & 34.