THE LUMBOSACRAL PLEXUS 



1049 



The iliac branch (ramus cutaneus lateralis) pierces the Internal and External 

 oblique muscles immediately above the crest of the ilium, and is distributed to the 

 integument of the gluteal region, behind the lateral cutaneous branch of the last 

 thoracic nerve (Fig. 775). The size of this nerve bears an inverse proportion to 

 that of the lateral cutaneous branch of the last thoracic nerve. 



The hypogastric branch (ramus cutaneus anterior} (Fig. 770) continues onward 

 between the Internal oblique and Transversalis muscles. It then pierces the 

 Internal oblique, and becomes cutaneous by perforating the aponeurosis of the 

 External oblique, about an inch (2.5 cm.) above and a little laterad of the external 

 abdominal ring, and is distributed to the integument of the hypogastric region. 

 The iliohypogastric nerve communicates with the last thoracic and ilioinguinal 

 nerves. 



FIG. 769. The lumbar plexus and its branches. 



The Ilioinguinal Nerve (n. ilioinguinalis'} (Figs. 769 and 770), smaller than the 

 preceding, arises with it from the first lumbar nerve. It emerges from the lateral 

 border of the Psoas magnus muscle just below the iliohypogastric nerve, and, 

 passing obliquely across the Quadratus lumborum and Iliacus muscles, perforates 

 the Transversalis near the fore part of the crest of the ilium, and communicates 

 with the iliohypogastric nerve between that muscle and the Internal oblique. 

 The nerve then pierces the Internal oblique, distributing muscular branches (rami 

 musculares] to it, and, accompanying the spermatic cord through the external 

 abdominal ring, is distributed to the integument of the upper and inner part 

 of the thigh, to the skin covering the root of the penis, and to the scrotum in the 



