THORACIC NERVES 



291 



The deep branch of the radial nerve is in the back of the forearm with the 

 dorsal interosseous artery; they do not extend below the wrist. 



(For the distribution of nerves to the principal joints, see page 74.) 



THORACIC NERVES (FIG. 186) 



There are twelve pairs of thoracic 

 nerves: 



Posterior divisions.' These send 

 branches to muscles and skin of the 

 back. 



Anterior divisions. These form 

 the intercostal nerves; the first assists 

 in the formation of the brachial 

 plexus. All run in the grooves under 

 the borders of the ribs, supplying in- 

 tercostal muscles, also the skin over 

 the muscles. The lower ones also 

 supply upper abdominal muscles and 

 skin. They accompany intercostal 

 arteries. 



LUMBAR NERVES 



There are five pairs of Lumbar 

 Nerves. 



Posterior divisions. These send 

 branches to muscles of the back; and 

 skin of the back, hip, and sacral region. 



FIG. 187. THE FEMORAL 

 NERVE. 



i, Femoral nerve; 2, 3, small 

 nerves from lumbar plexus; 4, 5, 



Anterior divisions. I he upper three 6,7,8,9,10, u, n, branches of 

 and a portion of the fourth form the f emoral erve : I2 I2 > '3 '4, 



long saphenous nerve and its 



lumbar plexus. The remainder of the branches; 15, obturator nerve; 16, 

 e j A.-L. i- i c j.1- .crii. r r 7 J 8, 19, branches of obturator 



fourth and th? whole of the fifth form ne ; ve; f a 2I> lumbo-sacral cord; 



the lumbo-sacral cord (Fig. 187). 2 3, external cutaneous nerve.- 



The lumbar plexus. This plexus 



lies within thebdomen, in the substance of the psoas muscle. Its 

 branches supply abdominal walls, and front and sides of the thigh 

 (also in temagumef both regions). They are all given off in the 



t.anoenbd 



Branches: the principal are: 



