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The Dissection Of The Oblique Or External And The Direct Or Internal Inguinal Herniae

Sources: Surgical Anatomy

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. 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 canal, traversing this canal 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 canal, H h, by an interval equal to the bulk of the

hernia. While the hernia occupies the canal, F H, without projecting

through the external ring, H, it is named "incomplete." When it has

passed 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 scrotum, 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 canal, at length terminates

in the scrotum.

The external inguinal hernia having entered the canal, 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 canal, even as far as the

testicle in the scrotum. 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 testicle is invariably found below it.

This fact is accounted for by the circumstance, that the lower end of

the spermatic envelopes is attached so firmly to the coats of the

testicle 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 vaginalis.

The external form of inguinal hernia is, comparatively speaking, but

rarely seen in the female. When it does occur in this sex, its position,

investments, and course through the inguinal canal, 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

testicle 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 circumstance 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


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 pass 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 canalis abdominalis aperturam internam

transit, tunicam vaginalem communem intrare nequit; parietem autem

canalis abdominalis internum aponeuroticum, in quo fovea inguinalis

interna, et qui ex adverso annulo abdominali est, ante se per annulum

trudit." (Comment, ad illust. 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 passes; 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 canal. 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 circumstance, 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.



A. That part of the ilium which abuts against the sacrum.

B. The spine of the ischium.

C. The tuberosity of the ischium.

D. The symphysis pubis.

E. Situation of the anterior superior iliac spine.

F. Crest of the ilium.

G. Iliacus muscle.

H. Psoas magnus muscle supporting the spermatic vessels.

I. Transversalis muscle.

K. Termination of the sheath of the rectus muscle.

L1 L2 L3. The iliac, transverse and pelvic portions of the transversalis


M M. The peritonaeum lining the groin.

N. The epigastric vessels lying between the peritonaeum, M, and the

transversalis fascia, L2. O. The umbilical ligament.

P. The neck of the sac of an external inguinal hernia formed before the

spermatic vessels.

Q. An interval which occasionally occurs between the umbilical ligament

and the epigastric artery.

R and Q. Situations where the direct inguinal hernia occurs when, as in

this case, the umbilical ligament crosses the space named the

internal fossa--the triangle of Hesselbach.

S. Lower part of the right spermatic cord.

T. The bulb of the urethra.

U. External iliac vein covered by the peritonaeum.

V. External iliac artery covered by the peritonaeum.

W. Internal iliac artery.

X. Common iliac artery.

Abdomen, showing bones, blood vessels, muscles<br />
<br />
and other internal organs

PLATE 33.--The External Inguinal Hernia.

A. Anterior iliac spinous process.

B. The umbilicus.

C. Fleshy part of the external oblique muscle; c, its tendon.

D. Fleshy part of the internal oblique muscle; d, its tendon.

E. Transversalis muscle; e, the conjoined tendon.

F f. The funnel-shaped sheath of the spermatic vessels covering the

external hernia; upon it are seen the cremasteric fibres.

G g. The peritonaeal covering or sac of the external hernia within the


H. The external abdominal ring.

I. The crista pubis.

K k. The saphenous opening.

L. The saphena vein.

M. The femoral vein.

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

O. The anterior crural nerve.

P. The epigastric vessels overlaid by the neck of the hernia.

Q Q. The sheath of the femoral vessels.

R. The sartorius muscle.

S. The iliacus muscle.

Abdomen and leg, showing blood vessels, muscles<br />
<br />
and other internal organs

PLATE 34.--The Internal Inguinal Hernia.

The letters indicate the same parts as in Plate 33

Abdomen and leg, showing blood vessels, muscles<br />
<br />
and other internal organs