Bardeen, Variations in the Lumbar Plexus. igy 



down through the psoas muscle and across to the pubis. The 

 crural branch suppHes the skin of the upper leg just below 

 Poupart's ligament, the genital branch passing down the in- 

 guinal canal and anastomosing with the inguinal nerve suppHes 

 a region similar to that innervated by the latter. The extent of 

 distribution of the genital is inversely proportional to that of 

 the inguinal. 



There is usually a branch of communication rom the ven- 

 tral primary division of the twelfth thoracic nerve to that of the 

 first lumbar. A similar branch from the first lumbar to the 

 second is even more constant. There may be a similar connec- 

 tion between the second and third and between the third and 

 fourth lumbar nerves. There is thus a sort of "collector" 

 nerve formed which may run from the eleventh thoracic to the 

 fourth lumbar nerve. So long a course however is rare. In- 

 deed it is doubtful if nerve fibers often pass thus over more than 

 two segments. Certainly the majority usually enter the nerves 

 arising from the segment immediately below. 



From this "collector" nerve and from branches springing 

 directly from the second, third, fourth and rarely the fifth lum- 

 bar nerves arise the obturator and the antenor cniral nerves. 



The obturator arises from the ventral surfaces of these 

 nerves. Passing through the obturator foramen it supplies the 

 adductor muscles of the leg and some of the skin of the inner 

 thigh. 



The anterior crural nerve arises mainly from the dorsal sur- 

 faces of the spinal nerves and passing over the iliac crest sup- 

 plies the extensor muscles of the thigh and the skin of the 

 outer, middle and inner ventral regions of the upper leg 

 and of the inner side of the lower leg. The nerve supply- 

 ing the outer side of the thigh (the external cutaneous) usually 

 arises separately from the main trunk ; the other cutaneous 

 nerves of the thigh may do so. Sometimes an "accessory 

 obturator" runs over the pubic crest to supply the pectineus 

 muscle and anastomose with the obturator. 



