468 LUMBAR NERVES. 



given off at about the middle of the arch of the rib. The first inter- 

 costal nerve has no cutaneous branch. The cutaneous branches of the 

 second and third intercostal nerves are named, from their origin and 

 distribution, inter costo-humercd. 



The FIRST INTERCOSTO-HUMERAL NERVE is of large size ; it pierces 

 the external intercostal muscle of the second intercostal space, and di- 

 vides into an internal and an external branch. The internal branch is 

 distributed to the integument of the inner side of the arm. The ex- 

 ternal branch communicates with the nerve of Wrisberg, and divides 

 into filaments which supply the integument upon the inner and poste- 

 rior aspect of the arm as far as the elbow. This nerve sometimes takes 

 the place of the nerve of Wrisberg. 



The SECOND INTERCOSTO-HUMERAL NERVE is much smaller than 

 the preceding ; it emerges from the external intercostal muscle of the 

 third intercostal space between the serrations of the serratus magnus 

 muscle, and divides into filaments which are distributed to the integu- 

 ment of the shoulder. One of these filaments may be traced inwards 

 to the integument of the mamma. The two intercosto- humeral nerves 

 not unfrequently communicate previously to their distribution. 



The cutaneous branches of the fourth and fifth intercostal nerve 

 send anterior twigs to the integument of the mammary gland and pos- 

 terior filaments to the scapular region of the back. The cutaneous 

 branches of the remaining intercostal nerves reach the surface between 

 the serrations of the serratus magnus muscle above and the external 

 oblique below, and each nerve divides into an anterior and a posterior 

 branch ; the former being distributed to the integument of the antero- 

 lateral, and the latter to that of the lateral part of the trunk. 



The cutaneous branch of the last dorsal nerve is remarkable for its 

 size (n. clunium superior anticus) ; it pierces the internal and external 

 oblique muscles, crosses the anterior part of the crest of the ilium, and 

 is distributed to the integument of the gluteal region as low down as 

 the trochanter major. 



LUMBAR NERVES. 



There are five pairs of lumbar nerves, of which the first makes its 

 appearance between the first and second lumbar vertebrae, and the 

 last between the fifth lumbar and the base of the sacrum. The antenor 

 branches increase in size from above downwards. They communicate at 

 their origin with the lumbar ganglia of the sympathetic, and pass oblique- 

 ly outwards behind the psoas magnus or between its fasciculi, sending 

 twigs to that muscle and to the quadratus lumborum. In this situa- 

 tion each nerve divides into two branches, a superior branch which as- 

 cends to form a loop of communication with the nerve above, and an 

 inferior branch which descends to join in like manner the nerve below, 

 the communications and anastomoses which are thus established con- 

 stituting the lumbar plexus. 



The posterior branches diminish in size from above downwards ; they 



