NEUROLOGY 285 



alis inferior, or brachialis anticus, and then divides into two branches. 

 The first and largest branch passes between the two pronator muscles 

 giving branches to the pronator profundus, or pronator longus, and 

 the flexor digitorum profundus muscle. This nerve then passes 

 anteriorly along the tendon to the base of the digit, and, on the 

 dorsal side, joins the other branch of the median nerve. At this 

 point there is often a plexus, and at the point of fusion of the ulnar 

 nerve on the ulnar side there may also- be a small plexus. These 

 plexuses mainly supply the skin of these regions. The second 

 branch, passes forward, crosses the extensor carpi radialis and lies 

 just below the pronator profundus, or pronator longus, giving 

 branches to the skin. It passes downward on the radial side of the 

 ulnar and supplies the muscles of that part; it then continues 

 down the hand. Branches are given off to the extensor proprius 

 pollicis, the interosseous dorsalis, the flexor digitorum, and to the 

 skin between the thumb and the forefinger. 



The intercostal nerves (Fig. 70, No. 18) are given off from the 

 spinal cord of the dorsal region. The superior branches are small 

 and supply the superior dorsal region. The inferior branches lie 

 one behind each rib, innervate the intercostal muscles, and give 

 a few twigs to the superficial thoracic muscles. 



The Lumbo-sacral, or Crural, Nerve Plexus. The crural plexus 

 (Fig. 70, No. 35 and 36) is made up of trunks from the last two 

 lumbar and first four sacral spinal nerves. There are two portions 

 of this plexus separated by a considerable distance. 



The anterior portion (Fig. 70, No. 35) consists of the lumbar 

 nerves and a portion of the first sacral nerves. The fusion takes 

 place on the bony ridge that separates the lumbar from the sacral 

 region. 



The posterior portion (Fig. 70, No. 36) consists of a part of the 

 first sacral and all of the three succeeding nerves. 



The anterior nerve of this plexus is distributed to the abdominal 

 muscles. An anterior branch is given off to the sartorius. A large 

 cutaneous branch enters between the sartorius and the ilio-trochan- 

 teric eminence, and supplies the outer and the upper surface of the 

 upper thigh region. Several short branches are given off from the 

 middle, or main, mass of the crural plexus to the ilio-trochanteric, 

 or gluteal, muscle. Another nerve passes over the side of the 

 sartorius adjacent to the femoro-tibialis, or extensor femoris, 

 and supplies the ilio-tibialis, or gluteus primus. The rest of this 



