THE ABDOMEN. 



377 



The external oblique arises from the eight lower ribs. Its posterior portion 

 passes almost directly downward to insert into the anterior half of the crest of the 

 ilium. It is crossed obliquely by the anterior margin of the latissimus dorsi muscle 

 a short distance above the crest, thus leaving a triangular space between them called 

 Petit 's triangle (trigonum lumbale) (see page 394). As the external oblique 

 approaches the linea semilunaris and anterior superior spine it becomes tendinous, 

 its fibres being nearly but not quite parallel with Poupart" s ligament. Its lower edge 

 forms Pouparf s ligament (ligamentum inguinale) and continues down on the thigh 

 as the fascia lata. Its inner portion, above and external to the spine of the pubis, 

 divides to form the external abdominal ring for the passage of the spermatic cord. 

 The outer side of the opening is called the external pillar or column; it is continuous 

 with Poupart' s ligament, inserts into the spine of the pubis, and is prolonged along 

 the iliopectineal line for a short distance (2 cm.) to form Gimbernat' s ligament. 



Latissimus dorsi 



Internal oblique 



Crest of ilium 

 Anterior superior spine 



Aponeurosis of external 

 oblique cut and turned down 



Shelving edge of 

 Poupart's ligament 



Cremaster arising from 

 Poupart's ligament 



Attachment of fibres of 

 cremaster to the pubis 



External oblique turned 

 back 



Arching fibres of 

 internal oblique 

 The conjoined tendon of 

 the internal oblique and 

 transversal is 



Spine of pubis 



FIG. 389. Internal oblique muscle. 



Sometimes it is continuous upward and inward to the median line on the sheath of 

 the rectus, forming what has been called the triangular fascia (Colles). The inner 

 side is called the internal pillar or column. It inserts into the crest of the pubis. 

 The transverse fibres passing from one pillar or column to the other are called 

 intercolumnar fibres. 



The internal oblique (Fig. 389) arises from the lumbar aponeurosis, the anterior 

 two-thirds of the crest of the ilium, and the outer half of Poupart's ligament. It inserts 

 into the lower three ribs and, through the sheath of the rectus and conjoined ten- 

 don, into the linea alba, the crest and spine of the pubis, and iliopectineal line for about 

 4 cm. The fibres arising from the lumbar aponeurosis and the posterior portion of the 

 iliac crest pass upward and inward. Those from the region of the anterior superior iliac 

 spine radiate like a fan ; the lower ones, together with the fibres arising from the 

 outer half of Poupart's ligament, arch over the cord and end in the conjoined tendon. 

 Some fibres are continuedjiown over the cord, forming the cremader muscle. The 



