THE MUSCLES OF THE ABDOMINAL WALL. 



479 



transversus. It arises from, (1) the lumbo-dorsal fascia, (2) the anterior two- 

 thirds of the iliac crest, and (3) the lateral half of the inguinal ligament. 



It runs for the most part, upwards and forwards, and its highest fibres are 

 inserted directly into the last three ribs. The rest of the fibres end in an extensive 

 aponeurosis, broader above than below, which splits along the linea semilunaris, 

 to form, along with the aponeuroses of the obliquus externus and transversus muscles, 



FIG. 425. THE EIGHT OBLIQUUS INTERNUS ABDOMINIS. 



the sheath of the rectus abdominis, and is inserted into the seventh, eighth, and ninth 

 costal cartilages, and into the linea alba from the xiphoid process to the symphysis 

 pubis. The fibres arising from the inguinal ligament join with those of the 

 transversus muscle having a similar origin to form the falx aponeurotica inguinalis 

 (O.T. conjoined tendon), which passes altogether anterior to the rectus muscle, to 

 be attached to the pubic crest and tubercle, and to the ilio-pectineal line. 



The obliquus internus is limited above by the inferior margin of the thorax 



