THE LUMBAR PLEXUS. 



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an inch above and a little to the outer side of the external abdominal ring, and is 

 distributed to the integument of the hypogastric region. 



The ilio-hypogastric nerve communicates with the last dorsal and ilio-inguinal 

 nerves. 



The Ilio-inguinal Nerve, smaller than the preceding, arises with it from the first 

 lumbar nerve. It emerges from the outer border of the Psoas just below the ilio- 

 hypogastric, 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 ilio-hypogastric nerve between that muscle and the 

 Internal oblique. The nerve then pierces the Internal oblique, distributing fila- 

 ments 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, 

 and to the scrotum in the male and to the labium majus in the female. The size of 

 this nerve is in inverse proportion to that of the ilio-hypogastric. Occasionally it 

 is very small, and ends by joining the ilio-hypogastric; in such cases a branch 

 from the ilio-hypogastric takes the place of the ilio-inguinal, or the latter nerve 

 may be altogether absent. 



FIG. 417. The lumbar plexus and its branches. 



The Genito-crural Nerve arises from the first and second lumbar nerves. It 

 passes obliquely through the substance of the Psoas, and emerges from its inner 

 border at a level corresponding to the intervertebral substance between the third 

 and fourth lumbar vertebrte ; it then descends on the surface of the Psoas muscle, 

 under cover of the peritoneum, and divides into a genital and a crural branch. 



