i / THE MUSCLES OF THE ABDOMINAL WALL. 401 
and attaches the fascia transversalis and fascia iliaca; the inner part forms the floor 
of theinguinalcanal. At its inner end a triangular band of fibres is reflected horizon- 
tally backwards to the ilio-pectineal line, forming Gimbernat’s ligament, the outer 
edge of which limits internally the crural ring. The femoral vessels in the femoral 
sheath enter the thigh beneath Poupart’s hgament, in front of the psoas muscle. 
The external abdominal ring, the place of exit of an inguinal hernia, is a split in 
the aponeurosis of the obliquus externus, just above the spine of the pubis. It 
transmits the spermatic cord, or round ligament of the uterus, covered by the 
cremaster muscle or cremasteric fascia. The opening is of considerable extent, and its 
edges are drawn together by a thin fascia, strengthened superficially by a number 
of arched and horizontal fibres, the intercolumnar fibres, which arise from Poupart’s 
ligament and sweep inwards across the cleft in the aponeurosis. 
The margins of the ring constitute its pillars. The external pillar is narrow, 
and is formed from that part of the aponeurosis which joins the pubic spine, and is 
continuous with 
the inner end of 
Poupart’s — liga- 
ment. The in- 
ternal pillar is the 
part of the apo- 
neurosis internal OBLIQUUS INTERNUS 
to the ring which 
is attached to the 
crest and sym- 
physis of the recaes ie 
pubis. It 1s flat obliquus externus (cut) 
and broad. 
The inter- 
columnar fibres Genito-crural nerve 
and the pillars of 
the external ab- 
dominal ring are 
continuous with 
a thin tubular 
sheath, the inter- 
columnar or ex- 
ternal spermatic 
fascia, which forms an envelope for the spermatic cord or round ligament beyond 
the external abdominal ring. 
The triangular fascia, lastly, is a triangular band of fibres placed behind the 
internal pillar of the external abdominal ring. It consists of fibres from the 
opposite external oblique aponeurosis, which, having traversed the linea alba, gain 
an insertion into the crest and spine of the pubis on the opposite side. 
The obliquus externus muscle is superficial in almost its whole extent. It is 
overlapped posteriorly by the latissimus dorsi muscle, but may be separated from 
it just above the iliac crest by an angular interval (triangle of Petit). 
The obliquus internus abdominis, a broad thin sheet lying between the 
obliquus externus and the transversalis, arises from (1) the lumbar fascia, (2) the 
anterior half of the iliac crest, and (3) the outer half of Poupart’s lhgament. 
Directed for the most part upwards and forwards, its highest fibres are inserted 
directly into the last three ribs. The rest of the fibres form an extensive aponeurosis, 
broader above than below, which splits along the linea semilunaris, to form, along 
with the aponeuroses of the obliquus externus and transversalis muscles, the sheath 
of the rectus, and is thereafter inserted into the seventh, eighth, and ninth costal 
cartilages, and into the linea alba from the ensiform cartilage to the symphysis 
pubis. The fibres arising from Poupart’s ligament join with those of the trans- 
versalis muscle having a similar origin to form the conjoint tendon, which passes 
altogether in front of the rectus muscle, to be attached to the pubic crest and 
spine and to the ilio-pectineal line. 
26 
OBLIQUUS EXTERNUS 
Aponeurosis of 
obliquus 
externus (cut) 
Twelfth thoracic 
nerve 
Ilio-hypogastric nerve 
Ilio-inguinal nerve 
Triangular fascia 
Spermatic cord 
‘ Suspensory liga- 
Saphenous ng 7 : EAS) 
a Penns ment of penis 
Intercolumnar 
fascia 
Dartos muscle 
Internal saphenous vein 
Fic. 296.—THEe Groin. The structures seen on removal of part of the 
obliquus externus. 
