ee ; ; E 
THE LUMBAR PLEXUS. 599 
ilio-inguinal. The lower branch of the first joins the upper branch of the second 
nerve, to produce the genito-crural nerve. ‘The lower branch of the second nerve, 
the whole of the third, and that part of the fourth nerve engaged in the con- 
stitution of the plexus divide each into two unequal parts—smaller anterior and 
larger posterior parts. The smaller anterior portions combine together to form 
the obturator nerve, which is thus formed by the second, third, and fourth lumbar 
Vena caval opening (Esophageal opening Central tendon (middle part) 
. \ / 
Diaphragm (right crus) 
_Middle areuate ligament 
~ Aortic opening 
Central tendon 
(eft part) 
Diaphragm (left 
Central tendon (right part) aes 
Diaphragm (costal fibres) 
Internal arcuate ligament DAM 
External arcuate ligament 
LAST THORACIC 
Eq NERVE 
+—End of last rib 
LUMBAR NERVE I. 
ILIO-HYPUGASTRIC 
LUMBAR NERVE II. 
End of last rib 
LAST THORACIC NERVE 
Ant. layer of lumbar fascia 
Lumbar fascia- 
ILIO-HYPOGASTRIC- 
Lumbar vessels and sympa- 
hetic communicating nerves 
ILI0-INGUINAL™ 
IL10o-INGUINAL 
Quadratus 
3 wal lumborum 
LUMBAR NERVE III. 
Quadratus lumborum 
GENITO-CRURAL 
7 LUMBAR NERVE IV. 
IXTERNAL CUTANEOUS NERVE 4U I I 
Psoas magnus 
Tliacus 
LuMBO-SACRAL CORD—* 
EXTERNAL CUTANEOUS 
NERVE 
ANT. CRURAL NERVE 
GENITO-CRURAL NERVE 
ANTERIOR CRURAL NERVE 
SCHEIN) SEDER OBTURATOR NERVE 
GREAT SCIATIC NERVE GREAT SCIATIC NERVE 
\ OBTURATOR NERVE} 
\ Adductor longus (origin) 
Adductor brevis (origin) 
| Gracilis (origin) 
Adductor magnus (origin) 
Pectineus (cut) 
| 
1 
SUPERFICIAL BRANCH OF OBTURATOR NERVE 
| DEEP BRANCH OF OBTURATOR NERVE 
Obturator externus 
| | 
Fic. 440.—Vigew oF THE PosTERIOR ABDOMINAL WALL, TO SHOW THE MUSCLES AND THE NERVES OF 
THE LUMBO-SACRAL PLEXUS. 
nerves. The root from the second nerve is not always present. The larger 
posterior portions of the same nerves combine together to form the anterior 
crural nerve. From the back of the posterior parts of the second and third 
nerves, the external cutaneous nerve arises. The nerves also provide, near their 
origins, irregular muscular branches, for the psoas and quadratus Jumborum 
muscles. The following is a list of the nerves which spring from the lumbar 
plexus (Figs. 439 and 440) :-— 
Ae 
