600 ^HE LUMBAR NERVES. 



and anterior crural nerves, and a connecting branch to the fifth 

 nerve. 



The BRANCHES of this plexus form two sets, which are distributed, 

 one to the lower part of the wall of the abdomen, the other to the fore 

 part and inner side of the lower limb. In the former set are the ilio- 

 hypogastric and ilio-inguinal nerves, and part of the genito-crural ; and 

 to the latter belong the remaining part of the genito-crural nerve, the 

 external cutaneous, the obturator, and the anterior crural nerves. 



Ilio-hjrpogastric and ilio-ingiiiual nerves. 



These nerves are the upper two branches from the lumbar plexus ; 

 they are both derived from the first lumbar nerve, and have a nearly 

 similar distribution. They become subcutaneous by passing between 

 the broad muscles of the abdomen, and through the outer one, and end 

 in the integument of the groin and scrotum in the male, and the labia 

 pudendi in the female, as well as in the integument covering the gluteal 

 muscles. The extent of distribution of the one is inversely proportional 

 to that of the other. 



The ilio-hypogastric nerve, emerging from the upper part of the 

 psoas muscle at the outer border, runs obliquely over the quadratus 

 lumborum to the iliac crest, and there perforating the transverse muscle 

 of the abdomen, gets between that muscle and the internal oblique, 

 and divides into an iliac and hypogastric branch. 



{a) The iliac branch pierces the attachment of both oblique muscles, immedi- 

 ately above the iliac crest, and is lost in the integnment over the gluteal muscles, 

 behind the distribution of the lateral cutaneous branch of the last dorsal nei-ve. 



(&) The hypogastric or ahdominal branch passes on between the transverse and 

 internal oblique muscles, and is connected vrith the ilio-inguinal nerve near the 

 iliac crest. It then perforates the internal oblique muscle, and, piercing the 

 aponeurosis of the external oblique, a little above the superficial inguinal opening, 

 is distributed to the skin of the abdomen above the pubes. 



The size of the Uiac branch of this nerve varies inversely with that of the 

 lateral cutaneous branch of the twelfth dorsal. The hjT)ogastric branch is not 

 unfrequently joined -with the last dorsal nerve between the muscles, near the 

 crest of the innominate bone. 



The ilio-inguinal nerve, smaller than the preceding, supplies the 

 integument of the groin. Descending obliquely outwards over the 

 quadratus lumborum, it crosses the fibres of the iliacus muscle, being 

 placed lower down than the iho-hypogastric : it then perforates ' the 

 transverse muscle further forwards than the ilio-hypogastric ; com- 

 municating with that nerve between the abdominal muscles. Then 

 piercing the internnl oblique muscle, it descends in the inguinal canal, 

 and emerging at the superficial inguinal ring, is distributed to the skin 

 upon the groin, as well as to that upon the scrotu.n and penis in the 

 male, or the labium pudendi in the female, communicating with the 

 inferior pudendal nerve. In its progress this serve furuishes branches 

 to the internal oblique muscle. 



Varieties. — The ilio-inguinal nerve occasionally arises from ilie loop connect- 

 ing the first and second lumbar nerves. It is sometimes small, and ends near the 

 iliac crest by joining the ilio-hypogastric nerve ; in which case the latter gives 



