THE NERVOUS SYSTEM. 223 



cutaneous and furnishes the sensation experienced when 

 one strikes what is popularly called his 'funny bone," 

 but what is really the ulnar nerve. It then passes 

 down the ulnar side of the forearm, supplying some 

 of the flexor muscles, and finally divides to supply 

 the fourth and fifth digits. The ventral branches 

 of the remaining thoracic nerves encircle the body, 

 supplying the muscles and skin of those regions. 



The lumbar plexus (Fig. 102) is composed of the 

 anastomosing of the ventral branches of the seven 

 lumbar nerves. As in the cervical and thoracic nerves, 

 the lumbar nerves divide into dorsal and ventral branches 

 immediately without the intervertebral foramen. The 

 former supply the muscles and skin of the back. The 

 first five ventral branches are joined to each other by 

 a delicate nerve-cord. In order to display this plexus, 

 the entire ventral and lateral abdominal wall should 

 be cut away and the specimen securely nailed to the 

 tray on its back. The adipose tissue and muscles lying 

 on either side of the bodies of the lumbar vertebrae 

 must be carefully picked away until the roots of the 

 nerves are apparent. They may then be easily followed 

 distad. 



The iliohypogastric nerve is the ventral branch of 

 the first lumbar nerve. It supplies the muscles of 

 the abdomen. This nerve and the two next described 

 are scarcely as large in diameter as an ordinary pin. 

 The ilio-inguinal nerve is the ventral branch of the 

 second lumbar nerve. Within two centimeters of its 

 origin it divides into two branches, the cephalic of 

 which supplies the rectus and transverse muscles and 

 the caudal supplies structures in the inguinal region. 

 The lumbo -inguinal nerve is the ventral branch of the 

 third lumbar nerve. Its cephalic branch supplies the 



