Abdomen. 171 



supplied by the terminal and the lateral cutaneous 

 branches of the lower intercostal nerves, by the ilio-hypo- 

 gastric, and to a very slight extent, by the ilio-inguinal. 

 2. Muscles of the Abdomen. The external 

 oblique, arising from the outer surfaces and lower borders 

 of the eight lower ribs, is directed downwards and inwards 

 and terminates, partly in the anterior half of the outer lip 

 of the crest of the ilium, and partly in the aponeurosis 

 to be described presently. The internal oblique, the 

 general direction of which is upwards and inwards, arises 

 from the outer half of Poupart's ligament, from the ante- 

 rior two-thirds of the middle lip of the crest of the ilium 

 and from the posterior lamella of the lumbar fascia, and 

 terminates in an aponeurosis. The transversalis, from 

 the outer third of Poupart's ligament, from the anterior 

 three-fourths of the inner lip of the crest of the ilium, from 

 the inner surfaces of the six lower ribs and from the lum- 

 bar fascia, is continuous with an aponeurosis also. The 

 rcctus muscle extends from the crest and anterior surface 

 of the pubes to the cartilages of the fifth, sixth and seventh 

 ribs. It is traversed by three tendinous intersections 

 called the linece transverse, which occupy the anterior 

 surface only of the muscle and are adherent to its sheath. 

 These transverse lines probably represent the membran- 

 ous partitions between the vertebrate segments found in 

 fishes, an arrangement whereby the body is divided into 

 zones myomeres by partitions myocommata. Pyra- 

 midalis a small muscle contained in the sheath of the 

 rectus and arising from the front of the pubic bone, and 

 inserted into the linea alba midway between the umbilicus 

 and the pubes. 



Actions of the Abdominal Muscles. When 

 the pelvis is fixed, the abdominal muscles flex the trunk 

 directly to the front when the muscles on both sides act 



