650 



SPINAL NERVES. 



sometimes, also, it furnishes a -part of the accessory obturator. The fourth 

 nerve completes the formation of the anterior crural, and the obturator, and 

 gives off a communicating branch to the fifth lumbar ; sometimes it also fur- 

 nishes part of the accessory obturator. 



The branches of the lumbar plexus are the 



Ilio-hypogastric. Obturator. 



Ilio-inguinal. Accessory obturator. 



Genito-crural. Anterior crural. 

 External cutaneous. 



These branches may be divided into two groups, according to their mode of 

 distribution. One group, including the ilio-hypogastric, ilio-inguinal, and part 

 of the genito-crural nerves, supplies the lower part of the parietes of the abdo- 



Fi-. 354. The Lumbar Plexus and its Branches. 



men; the other group, which includes the remaining nerves, supplies the fore 

 part of the thigh and inner side of the leg. 



The Ilio-hypogastric Nerve (superior musculo-cutaneous) arises from the first 

 lumbar nerve. It pierces the outer border of the Psoas muscle at its upper 

 part, and crosses obliquely in front of the Quadratus Lumborum to the crest 

 of the ilium. It then perforates the Transversalis muscle at its back part, and 

 divides between it and the Internal Oblique into two branches, iliac and hypo- 

 gastric. 



The iliac branch pierces the Internal and External Oblique muscles imme- 

 diately above the crest of the ilium, and is distributed to the integument of the 



