THE LUMBAR PLEXUS. 



1321 



Variations. The iliac branch may be absent, its place being taken by the lateral cutaneous 

 branch of the twelfth thoracic nerve. The hypogastric branch may inosculate with the twelfth 

 thoracic and may supply the pyramidalis muscle. 



3. THE ILIO-INGUINAL NERVE. 



The ilio-inguinal nerve (n. ilioinguinalis) (Fig. 1107) is the second branch of 

 the lumbar plexus and is somewhat smaller than the ilio-hypogastric. Its fibres 

 usually arise from the first lumbar nerve, with accessions from the twelfth thoracic. 



FIG. 1107. 



XII. rib 

 XII. thoracic nerve 



Quadratus lumborum 

 Psoas magnus 



External oblique 



Lateral cutaneous branch 



of XII. dorsal nerve 



Internal oblique 



Transversalis 



Ilio-hypogastric nerve 



Ilio-inguinal nerve 



Iliac branch of 

 ilio-hypogastric 



Lateral cutaneous branch 

 of XII. dorsal nerve 



External cutaneous nerve 



Anterior crural nerve 

 Genital branch of 

 genito-crural nerve 



Crural branch of 



genito-crural nerve 



Branches of middle 



cutaneous nerve 



I. lumbar ganglion 



Rami communicantes 



Aorta 



IV. lumbar nerve 



. lumbar ganglion 



. lumbar nerve 



irt of V. lumbar ganglion 



jnito-erural nerve 

 sacral ganglion 



sacral nerve 



sacral nerve 



sacral ganglion 



urator nerve 



essory obturator nerve 



) Hypogastric branches 

 ) of ilio-hypogastric nerve 



Ilio-inguinal nerve 



Branch of internal 

 cutatieous nerve 



Deep dissection, showing nerves arising from lumbar plexus and lower part 

 of sympathetic gangliated cord. 



Sometimes it arises entirely from the twelfth thoracic or from the second lumbar or 

 from the loop between the first and second lumbar nerves. It occasionally forms a 

 common trunk of considerable length with the ilio-hypogastric. In the early part 



