324 PRACTICAL ANATOMY. 



ous. The radial nerve accompanies the radial artery, 

 and is distributed to the muscles of the forearm and 

 thumb, and to the integument of the dorsal surface of 

 the thumb, index, and middle fingers. The posterior 

 interosseous pierces the supinator brevis, and descends 

 deeply along the posterior part of forearm, and termi- 

 nates above the wrist-joint in a ganglionic enlargement. 

 The musculo-spiral nerve sends off branches to the 

 muscles of the forearm and cutaneous branches to the 

 integument in the region of the elbow along its outer side. 



Dorsal Nerves. 



The dorsal nerves are smaller than any other spinal 

 nerves except the last sacral and coccygeal. They con- 

 sist of twelve pairs. The last pair emerge between the 

 last dorsal and first lumbar vertebra. They arise from 

 the cord on a higher plane than the foramina through 

 which they pass and divide into an anterior and posterior 

 branch. The anterior form the intercostal nerves. They 

 run between the intercostal muscles, send off a number 

 of branches to the wall of the chest, and terminate near 

 the sternum in the cutaneous branches, which supply the 

 skin and superficial structures at the anterior part of 

 chest. The posterior branches are distributed to the 

 muscles of the back and the integument. 



Lumbar Nerves. 



The lumbar nerves are five in number. The last 

 lumbar makes its exit between the last lumbar vertebra 

 and sacrum. The roots are very long and large, and 

 unite in the intervertebral foramina. As they emerge 

 they divide into smaller posterior and larger anterior 

 branches. The posterior branches are distributed to the 

 muscles of the back and the integument in this and the 

 gluteal region. The upper four lumbar nerves form the 



