136 ANTHROPOLOGY. 



last posterior nerves are very small, and are distributed to the integuments 

 of the glutöeal region. 



The anterior branches of the lumbar nerves are much larger than the 

 posterior, and increase in size as they descend. In the psoas magnus 

 muscle they unite with each other into a plexus. 



6. The Lumbar Plexus is long and somewhat triangular, situated along 

 the sides of the lumbar vertebra3, in front of their transverse processes, and 

 near the posterior surface of the psoas magnus muscle ; in addition to its 

 three principal and terminal branches, the anterior crural, the obturator, 

 and the lumbo-sacral, it gives off" some long superficial branches. 



The siqjcrfidal branches of the lumbar plexus supply the inferior portion 

 of the abdominal muscles and integuments, the integuments of the groin, 

 of the upper and outer part of the thigh, and also those of the inguinal and 

 pubic regions. The principal of these are the superior musculo-cutaneous 

 (external ilio-inguinal, ilio-bypogastric, ilio-scrotal), the middle musculo- or 

 inguino-cutaneous, the inferior musculo-cutaneous or external cutaneous^ and the 

 (jenito-crural. 



The anterior crural nerve arises in the lumbar plexus from the four 

 superior nerves, principally from the third and fourth ; it is destined to 

 supply the integuments on the anterior and inner sides of the lower extre- 

 mities, also extensors of the leg, and the principal flexors of the thigh or 

 hip-joint. It subdivides into a superficial and a deep fasciculus. The prin- 

 cipal branches of the superficial division are, the middle cutaneous, the 

 internal cutaneous, the vaginal branches to the sheaths of the vessels, and the 

 long saphena. The branches of the deep division are wholly muscular. 



The obturator nerve arises chiefly from the third and fourth lumbar, per- 

 forates the psoas muscle, and descends obliquely inwards to the inside of the 

 thigh, where it descends into two branches, an anterior and a posterior. 

 The anterior or superficial branches are lost in the graciles, adductor brevis, 

 pectinseus, and vastus externus. The posterior or deep branches supply the 

 obturator externus and adductor magnus ; one long branch extends to the 

 back part of the knee joint. 



The lumbo-sacral nerve is the largest branch of the lumbar plexus ; it is 

 formed by a large portion of the anterior division of the fourth, and the 

 whole of that of the fifth lumbar nerves ; enters the pelvis, and behind the 

 iliac vessels divides into two branches. Of these, the communicating is 

 inferior or anterior, and joins the first anterior sacral nerve, forming part 

 of the sacral plexus ; the other, posterior and superior, is the great or supe- 

 rior glutceal nerve. This has various muscular branches for the muscles of 

 the thigh. 



7. The Sacral Nerves are six pairs. They form their ganglions, and 

 divide within the spinal cord into anterior and posterior branches. The 

 posterior sacral nerves are very small, pass through the posterior sacral 

 foramen, and supply the muscles and integuments of the sacral and glutaeal 

 regions. 



The anterior sacral nerves are very large, especially the three superior ; 

 the three last are much smaller, and the sixth is very minute, and sometimes 

 842 



