THE ABDOMINAL WALL 205 



thoracic nerves. They become superficial between the 

 digitations of the external oblique muscle, and then each 

 divides into an anterior and posterior division. The posterior 

 divisions are small, and are directed backwards over the latis- 

 simus dorsi. The anterior divisions supply the external oblique 

 muscle and then run forwards, and a careful dissector may 

 trace them as far as the lateral margin of the rectus 

 abdominis. 



The lateral cutaneous branch of the last thoracic nerve differs 

 from the other members of the series. It does not divide 

 into an anterior and a posterior division, but descends to 

 supply the integument over the gluteal region. It pierces 

 the external oblique muscle, in a line with the other lateral 

 nerves, and is then directed downwards over the crest of the 

 ilium. It crosses the iliac crest from 25 to 50 mm. (one to 

 two inches) behind the anterior superior spine. 



The lateral branch of the ilio-hypogastric nerve also is dis- 

 tributed to the skin of the gluteal region. It pierces the 

 external oblique immediately above the iliac crest, which it 

 crosses usually opposite the tubercle which projects from the 

 external lip of the crest, about 60 to 65 mm. (about two and 

 a half inches) behind the anterior superior spine of the ilium. 



Arteriae Cutaneae. Some of the cutaneous arteries ac- 

 company the cutaneous nerves. Those which are associated 

 with the lateral cutaneous nerves are branches of the aortic 

 intercostal arteries, whilst those in relation to the anterior 

 cutaneous nerves are derived from the superior and inferior 

 epigastric arteries. 



In addition three small branches of the femoral artery 

 ramify in the superficial fascia of the groin. 



These are 



1. The superficial external pudendal. 



2. The superficial epigastric. 



3. The superficial circumflex iliac. 



They take origin in the thigh, a short distance distal to 

 the inguinal ligament, and, after piercing the cribriform fascia 

 or the fascia lata, diverge from each other in the superficial 

 fascia. 



Arteria Pudenda Externa Superfdalis. The superficial 

 external pudendal artery is directed medially, over the 

 spermatic cord. It gives branches to the skin of the scrotum 

 and inferior surface of the penis. 



