SYMPATHETIC SYSTEM 179 



humeral nerve, is of unusually large size. It crosses the axilla 

 and supplies the skin of the armpit, and the inner side of 

 the posterior surface of the arm as far as the elbow. 



Third thoracic nerve is a typical one, except that the pos- 

 terior half of the lateral cutaneous branch also extends into 

 the arm, and' supplies a small portion of the posterior surface 

 of the root of the limb. 



Fourth, fifth, and sixth thoracic nerves are typical. 



Seventh, eighth, ninth, tenth, and eleventh thoracic nerves at 

 the anterior ends of their intercostal spaces pierce the attach- 

 ment of the diaphragm and the transversalis abdominis, and 

 pass forwards between the latter and obliquus internus. " Their 

 anterior ends become cutaneous by piercing the sheath of the 

 rectus and the muscle itself. They supply the intercostal 

 muscles of their own spaces and the abdominal muscles, and 

 help to supply the diaphragm. Their cutaneous branches are 

 similar to those of the typical nerves. 



Twelfth thoracic nerve passes downwards under psoas and 

 then passes forwards, similarly to those just above it. It gives 

 off a large lateral cutaneous branch, which, passing down 

 between the abdominal muscles, becomes cutaneous just above 

 the iliac crest, and supplies the skin of the buttock as far 

 down as the great trochanter of the femur. 



The Sympathetic System. 



The sympathetic system consists of two long chains of 

 ganglia lying one on each side of the vertebral column, ex- 

 tending from the base of the skull to the coccyx. The ganglia 

 :are connected to the spinal cord by white rami communicantes 

 given off by some of the spinal nerves (second thoracic to 

 second lumbar and three or four sacral) as they emerge from 

 the inter vertebral foramina. The ganglia send grey rami com- 

 municantes back to the cord. Above, the chain ends by a plexus 

 of nerves sent into the cranial cavity on the internal carotid 

 artery, and below, the two terminal ganglia communicate with 

 one another. 



The ganglia send branches of supply to vessels, viscera, in- 

 voluntary muscles, and glands. 



