THE ABDOMEN 651 



of the ilio-pectineal line ; and (/) the anterior superior iliac 

 spine. 



Nerve-supply. — ^The lower five intercostal nerv^es and the sub- 

 costal nerve. 



Action. — (i) The two muscles, acting conjointly, diminish the size of the 

 abdominal cavity, and so compress the viscera, as in defaecation. (2) The 

 two muscles, acting conjointly from their origins, raise the front part of the 

 pelvis and flex it upon the thorax. (3) Acting conjointly from their inser- 

 tions, they flex the thorax upon the pelvis, the vertebral column being also 

 flexed in the lower thoracic and lumbar regions ; but, if the column is fixed, 

 the two muscles depress the lower eight ribs. (4) One muscle, acting from 

 its origin, is a lateral flexor of the pelvis. When it acts from its insertion it 

 flexes the thorax towards its own side and rotates it to the opposite side. 



The most of the fibres of the external oblique pass downwards 

 and forwards, coinciding in direction with those of the external 

 intercostal muscles. The only parts of the muscle which are free 

 are the part between the last rib and the iliac crest, and the 

 part opposite the pubic crest. The aponeurosis attains its greatest 

 width and strength at. and below, the level of the anterior superior 

 iliac spine, and it is narrowest opposite the umbilicus. Superiorly 

 it gives origin to fibres of the pectoralis major. Crossing the fibres 

 of the aponeurosis in an upward and inward direction there are 

 several superadded fibres. In the lower part of the abdominal wall 

 these are specially well marked, and are here spoken of as the 

 intercolumnar fibres. Under this name they spring from the outer 

 third of Poupart's ligament, whence they pass upwards and inwards 

 in a curved manner, the convexity being downwards. On arriving 

 at the upper and outer part of the external abdominal ring they 

 extend from one column to the other. They round off and close 

 the ring, and are prolonged upon the spermatic cord to form the 

 intercolumnar or external spermatic fascia. 



The following parts of the external oblique aponeurosis require 

 special description : Poupart's ligament, Gimbernat's ligament, 

 the triangular fascia, the external abdominal ring, and the linea 

 alba. 



Poupart's ligament, also known as the superficial femoral arch, 

 is the thickened lower border of the external oblique aponeiu"osis, 

 which is folded backwards. Externally it is attached to the 

 anterior superior iliac spine, and internally to the pubic spine, 

 from which it is reflected outwards and backwards upon the 

 ilio-pectineal line for fully i inch to form Gimbernat's ligament. 

 The ligament is curved, the convexity being directed down- 

 wards and outwards, which is due to the attachment of the 

 iliac lamina of the fascia lata to its lower border. The con- 

 vexity is greatest when the thigh is extended, abducted, and 

 rotated outwards, in which position the fascia lata on the front 

 of the thigh is tightened. 



Relations — Superficial. — Sldn ; Camper's and Scarpa's fasciae ; super- 

 ficial epigastric vessels, a little to the inner side of the centre; super- 

 ficial circumflex iliac vessels just below its outer part ; and the inguinal 



