80 Commentary on plates 30 & 31.
With the ideas of an inguinal canal thus naturally constituted, I need not hesitate to assert that the form, the extent, and the boundaries of the inguinal canal, as given by the descriptive anatomist, are purely conventional, and do not exist until after dissection; for which reason, and also because the form and condition of these parts so described and dissected do not appear absolutely to correspond in any two individuals, I omit to mention the scale of measurements drawn up by some eminent surgeons, with the object of determining the precise relative position of the several parts of the inguinal region.
The existence of an inguinal canal consisting, as I have described it, of funnel-shaped elongations from the several inguinal layers continued over the cord as far as the testicle, renders the adult male especially liable to hernial protrusions at this part. The oblique direction of the canal is, in some measure, a safeguard against these accidents; but this obliquity is not of the same degree in all bodies, and hence some are naturally more prone to herniae than others.
DESCRIPTION OF THE FIGURES OF PLATES 30 & 31.
PLATE 30.
A. The anterior superior iliac spine.
B. The umbilicus.
C. The spine of the pubis.
D. The external oblique muscle; d, its tendon. .
E. The internal oblique muscle; e, its tendon.
F. The transverse muscle; f, its tendon, forming, with e, the conjoined tendon.
G. The rectus muscle enclosed in its sheath.
H. The fascia spermatica interna covering the cord; h, its funnel-shaped extremity.
I, K, L, M. See Plate 31.
N. The femoral artery; n, its profunda branch.
O. The femoral vein.
P. The saphena vein.
Q. The sartorius muscle.
R. The sheath of the femoral vessels.
S. The falciform margin of the saphenous opening.
T. The anterior crural nerve.
U. The pubic portion of the fascia lata.
V. The iliac portion attached to Poupart's ligament.
W. The lower part of the iliacus muscle.
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.
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 constitutes 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 caecum 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 circumstances, 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 space, 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 constitute the inguinal canal, through which these vessels pass.