MUSCLES OP THE ABDOMEN. 189 



dens) is the external flat muscle of the abdomen. Its name is derived 

 from the obliquity of its direction, and the descending course of its 

 fibres. It arises by fleshy digitations from the external surface of 

 the eight inferior ribs. The five upper digitations being received 

 between corresponding processes of the serratus magnus, and the 

 three lower of the latissimus dorsi; it spreads out into a broad 

 aponeurosis, which is inserted into the outer lip of the crest of the 

 ilium for one half its length, the anterior superior spinous process of 

 the ilium, spine of the os pubis, pectineal line, front of the os pubis, 

 and linea alba. 



The lower border of the aponeurosis, which is stretched between 

 the anterior superior spinous process of the ilium and the spine of 

 the os pubis, is folded inwards, forming Poupart's ligament ; the in- 

 sertion into the pectineal line is Gimbernafs ligament. 



Just above the crest of the os pubis is the external abdominal ring, 

 a triangular opening formed by the separation of the fibres of the 

 aponeurosis of the external oblique. It is oblique in its direction, 

 and corresponds with the course of the fibres of the aponeurosis. It 

 is bounded below by the crest of the os pubis ; on either side, by the 

 borders of the aponeurosis, which are called pillars ; and above by 

 some curved fibres (inter-columnar), which originate from Poupart's 

 ligament, and cross the upper angle of the ring, so as to give it 

 strength. The external pillar, which is at the same time inferior, 

 from the obliquity of the opening is inserted into f the spine of the os 

 pubis ; the internal or superior pillar forms an interlacement with its 

 fellow of the opposite side over the front of the symphysis pubis. 

 The external abdominal ring gives passage to the spermatic cord 

 in the male, and round ligament in the female ; they are both in- 

 vested in their passage through it by a thin fascia derived from the 

 edges of the ring, and called inter- columnar fascia, or fascia sper- 

 matica. 



The pouch of inguinal hernia, in passing through this opening, re- 

 ceives the inter-columnar fascia, as one of its coverings. 



Relations. By its external surface with the superficial fascia and 

 integument, and with the cutaneous vessels and nerves, particularly 

 the superficial epigastric and superficial circumflex ilii vessels. It 

 is generally overlapped posteriorly by the latissimus dorsi. By its 

 internal surface with the internal oblique, the lower part of the eight 

 inferior ribs and intercostal muscles, the cremaster, the spermatic 

 cord in the male, and the round ligament in the female. 



The external oblique is now to be removed by making an incision 

 across the ribs, just below its origin, to its posterior border; and 

 another along Poupart's ligament and the crest of the ilium. Pou- 

 part's ligament should be left entire, as it gives attachment to the 

 next muscles. The muscle may then be turned forwards towards 

 the linea alba, or removed altogether. 



The internal oblique muscle (obliquus internus abdominis, ascen- 

 dens) is the middle flat muscle of the abdomen. It arises from the 

 outer half of Poupart's ligament, from the middle of the crest of the 



