146 HUMAN ANATOMY. 



MUSCLES OF THE ABDOMEN". 



OBLIQUUS EXTERNUS. Origin, lower borders of the eight 

 lower ribs; insertion, the lowermost muscular fibres, into the 

 anterior half of the iliac crest; the other muscular fibres, by a 

 broad aponeurosis, which joins the anterior half of the aponeu- 

 rosis of the internal oblique to form the anterior walls of the 

 sheath of the rectus, above into the ensiform cartilage, below 

 into the symphysis pubis. In the median line it blends with 

 its fellow of the opposite side to form the linea alba. A slit 

 in its lower portion above the pubic spine is called the external 

 abdominal ring. The lower thickened portion of the aponeu- 

 rosis stretching between the anterior superior iliac spine and 

 the pubic spine is called Poupart's ligament. A reflection from 

 it to the ilio-pectineal line is called Gimbernat's ligament; action, 

 flexes the pelvis on the thorax, or vice versa, and compresses the 

 viscera; nerves, lower intercostal, ilio-hypogastric, and ilio-in- 

 guinal. 



OBLIQUUS INTERNUS. Origin, from the outer half of Pou- 

 part's ligament, from the anterior two-thirds of the crest of the 

 ilium, and the posterior lamella of the lumbar fascia ; insertion, 

 above to the lower four costal cartilages, below, conjointly with 

 the tendon of the transversalis, into the os pubis and linea ilio- 

 pectinea, to form the conjoined tendon, and into the median 

 line (linea alba) by an aponeurosis extending from the sternum 

 and seventh and eighth costal cartilages to the pubis. This apo- 

 neurosis at its lower fourth consists of two united laminae passing 

 in front of the rectus muscle, but in its upper three-fourths it 

 divides, one lamina passing in front of the rectus and joining 

 the aponeurosis of the external oblique, the other passing behind 

 and joining the aponeurosis of the transversalis ; action, same as 

 the externus ; nerves, same as externus. 



TRANSVERSALIS. Origin, from outer third of Poupart's 

 ligament and anterior three-fourths of the crest of the ilium, 

 from the inner surface of the cartilages of the six lower ribs, and 

 from the spinous and transverse processes of the lumbar verte- 

 brae; insertion, by the conjoined tendon into the linea ilio-pcc- 

 tinea and crest of the os pubis; action and nerves, same as the 

 externus. 



RECTUS ABDOMINIS. Origin, by two tendons the outer 

 from the crest of the pubis, the inner interlacing with its fellow 

 of the opposite side; insertion, into the cartilages of the fifth, 

 sixth, and seventh ribs; action, depresses the thorax, flexes the 

 vertebral column, and, acting from above, flexes the pelvis upon 

 the vertebral column. 



