THE ABDOMEN 66i 



Deep Nerves of the Abdominal WalL— The lower ttve intercostal 

 nerves, after leaving the intercostal spaces, lie between the in- 

 ternal oblique and transversalis abdominis, and pass downwards 

 and forwards to the outer border of the rectus. Here they pierce, 

 in succession, the posterior wall of the sheath, the rectus, and the 

 anterior wall of the sheath, after which the}!- terminate in the 

 anterior cutaneous nerves. In their course they supply the two 

 oblique, the transversalis, and the rectus muscles. Each nerve 

 gives off a lateral cutaneous branch in the mid-axillary line. These 

 lateral cutaneous branches, having pierced the internal oblique, 

 appear between the slips of the external oblique and divide into 

 anterior and posterior branches. 



The subcostal nerve is the anterior primary div^ision of the 

 twelfth thoracic nerve. It is in series with the eleventh inter- 

 costal, but is not ranked as an intercostal nerve, inasmuch as it 

 lies along the lower border of the twelfth rib. It is commonly 

 spoken of as the last dorsal nerve. Its abdominal relations, course, 

 and distribution are similar to the preceding nerves, wdth an addi- 

 tional distribution to the pyramidalis abdominis. Its lateral 

 cutaneous or iliac branch, which is undivided, having pierced the 

 internal and external oblique muscles, descends over the anterior 

 part of the iliac crest, i inch behind the anterior superior iliac spine, 

 and is distributed to the integument of the anterior part of the 

 gluteal region as low as the great trochanter of the femur. 



The ilio-hypogastric nerve, having pierced the posterior part of 

 the transversalis abdominis a little above the iliac crest, furnishes 

 its iliac branch (lateral cutaneous), which perforates the internal 

 and external oblique, and, having crossed the iliac crest at the 

 junction of its middle and anterior thirds, is distributed to the 

 integument of the adjacent part of the gluteal region. The nerve 

 then continues its course forwards between the internal oblique 

 and transversalis, supplying branches to these muscles and com- 

 municating \\'ith the inguinal nerve. About i inch in front of the 

 anterior superior iliac spine it pierces the internal oblique, and runs 

 forwards between the Poupart fibres of that muscle and the external 

 oblique aponeurosis. Finally, it pierces that aponeurosis about 

 I inch above the external abdominal ring, and is distributed to the 

 integument of the suprapubic region, where it is in series with the 

 anterior cutaneous nerv^es. 



The inguinal nerve (ilio-inguinal), as it passes forwards, lies 

 internal to the inner lip of the iliac crest, beneath the transver- 

 salis and upon the iliac fascia and iliacus muscle. Near the anterior 

 part of the iliac crest it pierces the transversalis, and here com- 

 municates wdth the hypogastric branch of the ilio-hypogastric. It 

 subsequently perforates the Poupart fibres of the internal oblique, 

 after which it descends through the lower two-thirds of the inguinal 

 canal, and emerges through the external abdominal ring where it 

 lies external to the spermatic cord. Finally, it is distributed to 

 the integument of the inner side of the thigh in its upper third. 



