he 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 muscl