402 THE MUSCULAR SYSTEM. 
The obliquus internus is limited above by the costal arch. Its lower fibres, 
arching over the spermatic cord, assist in forming, externally, the anterior wall of 
the inguinal canal; internally, by means of the conjoint tendon, its posterior 
wall. 
Its lowest fibres are continued into the cremaster muscle, prolonged along the 
spermatic cord, through the inguinal canal. 
The cremaster muscle may be said to have an origin from the lower border of the 
obliquus internus, and from the middle of Poupart’s ligament. It forms a thin sheet, 
enveloping the testicle and spermatic cord ; its fibres are arranged in loops which arch 
over the cord, and are inserted into the fascia, and to a less extent (uppermost fibres) into 
the pubic spine. The muscle is more largely represented by fascia in the female, and 
constitutes the cremasteric fascia. 
The transversalis muscle arises (1) from the under surface of the costal 
cartilages of the lower six ribs, interdigitating with the origins of the diaphragm ; 
(2) from the lumbar fascia; (5) from the anterior half of the inner lip of the iliac 
crest; and (4) from the outer third of Poupart’s hgament. The muscular fibres 
OBLIQUUS EXTERNUS 
OBLIQUUS EXTERNUS 
OBLIQUUS INTERNUS OBLIQUUS INTERNUS (cut) 
TRANSVERSALIS MUSCLE 
OBLIQUUS INTERNUS (cut) 
Deep circumflex iliac artery Over deep epigastric artery 
Fascia transversalis 
Deep epigastric artery 
Conjoint tendon 
Over outer border of rectus abdominis 
Spermatic cord 
Triangular fascia 
Internal abdominal ring and _\\ 
infundibuliform fascia \ 
Spermatic cord passing — 
through cremaster muscle 
Fic. 297.—Tue Groin. The structures seen on reflexion of part of the obliquus internus. 
are directed for the most part horizontally forwards, and end in an aponeurosis 
which has a twofold insertion. (1) After forming (along with the aponeurosis of 
the obliquus internus) the posterior layer of the sheath of the rectus, the 
aponeurosis 1s attached to the ensiform cartilage and linea alba. (2) The lower 
fibres of the muscle are joined by the lower part of the obliquus internus to 
form the conjoint tendon, which passes in front of the lower part of the rectus 
muscle, to be inserted into the crest and spine of the pubis and the ilio-pectineal 
line. 
The transversalis muscle is separated by the lower intercostal nerves from the 
obliquus internus muscle, and is lined on its deep surface by the transversalis fascia. 
Its lower border forms a concave edge, separated from Poupart’s ligament by a 
lunular interval filled by the transversalis fascia, through which the spermatic 
cord uae at the internal abdominal ring, under cover of the obliquus internus 
muscle. 
The anterior muscles of the abdominal wall include the pyramidalis and — 
rectus abdominis, enveloped by the rectus sheath, on either side of the linea 
alba. 
The pyramidalis abdominis is a small triangular muscle arising from the pubic 
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