NERVES. 



the ends of the intercostal spaces they pierce the Diaphragm 

 and Transversalis, and run forward between the latter and 

 Obliquus internus; then passing between the Rectus and 

 its sheath (posterior layer) , and then through the Rectus and 

 its sheath (anterior layer), they supply (anterior cutaneous 

 branches) the midline from the ensiform cartilage to just below 

 the umbilicus. Muscular branches supply the Transversalis, 

 Obliqui, and Rectus. Lateral cutaneous branches descend 

 through the interdigitations of the External oblique, supplying 

 the loin down to the buttock; this branch of the eleventh ex- 

 tends over the iliac crest. [638] 



Twelfth Thoracic. This runs forward below the last rib, 

 under the Psoas, between the Quadratus lumborum and ex- 

 ternal arcuate ligament, then through the Transversalis and 

 between this and the Internal oblique, and then through the 

 Rectus and its sheath to (anterior cutaneous branch) the skin 

 midway between umbilicus and pubis. Muscular branches 

 supply the Transversalis, Obliqui, Rectus, and Pyramidalis. 

 The lateral cutaneous (iliac) branch descends anteriorly over the 

 iliac crest, to the buttock as far as in front of and below the 

 great trochanter. [638] 



Lumbar, Sacral, and Coccygeal. These form the Lumbo-sacral 

 plexus which, for convenience, is divided into the lumbar, sa- 

 cral (sciatic) , and pudendal plexuses. From the abdominal and 

 pelvic sympathetic cord each nerve receives gray rami com- 

 municantes, which cross the vertebrae under the Psoas. White 

 rami communicantes run from the first two (sometimes first 

 four) lumbar nerves to the upper part of the lumbar gangli- 

 ated cord; and from the third (sometimes second, third, and 

 fourth) sacral nerves, across the cord to the sympathetic pelvic 

 plexus. [639] 



LUMBAR PLEXUS. 



This lies deeply in the Psoas muscle, just in front of the 

 transverse processes, and is formed by the first three and 



[199] 



