ANATOMY IN A NUTSHELL. 101 



arm it lies to the side of the brachial artery and after crossing it t<> the inner 

 side of the artery. It lias no branches in the arm: at the elbow it gives off two 

 articular branches to the joint. 



After passing between the two heads of the Pronator radii teres it passes 

 to the distal extremity of the forearm where it passes under the anterior annular 

 ligament. In its course, in the forearm.it first lies between the Flexor sublimis 

 digitorum ami Flexor profundus digitorum, then between the tendon.- of the 

 Flexor sublimis digitorum and Flexor longus pollicis. It supplies all the mus- 

 cles in the first layer of the forearm except the Flexor carpi ulnaris. which are 

 the Pronator radii teres. Flexor carpi radialis. and Palmaris longus: it also sup- 

 plies the one muscle in the second layer which is the Flexor sublimis digitorum. 



LESSON XXV. 



The anterior interosseous nerve is given off just below and is accompanied 



by the anterior interosseous artery to the distal extremity of the forearm lying 

 on the interosseous membrane. The nerve is external to the artery being be- 

 tween the Flexor profundus digitorum and Flexor longus pollicis. This branch 

 supplies the Flexor longus pollicis, Pronator quadratus, and the outer side of 

 the Flexor profundus digitorum. It send- a branch to the wrist-joint, also one 

 to the anterior interosseous artery and to the interosseous membrane, to the 

 medullar}- arteries and to the periosteum of the radius and ulna. It i> worth 

 while to note that the anterior interosseous nerve is a branch from the median. 

 and the posterior Interosseous nerve is a branch of the musculo-spiral nerve, 

 while the anterior ami posterior interosseous arteries are both branches of the 

 same artery, viz.. the common interosseous. 



The palmar cutaneous branch of the median nerve arises in the distal third 

 of the forearm, passes between the Flexor carpi radialis and Palmaris longus, 

 pierces the deep fascia proximally to the anterior annular ligament and passes 

 over that ligament to the integument and fascia on the palmar surface of the 

 hand. It divides into two divisions, external and internal. The external one 

 supplies the skin over the ball of the thumb ami anastomoses with the anterior 

 cutaneous branches of the musculo-spiral and radial nerves. The internal 

 division supplies the integumenl on the palm, except that on the ulnar side and 

 anastomoses with the palmar cutaneous branches of the ulnar nerve. 



The median nerve then enters the hand beneath the anterior annular lig- 

 ament. It spreads out and is of a reddish color. It divides into external and 

 internal divisions. It lies upon the flexor tendons and is covered by integu- 

 ment, palmar fascia, and the superficial palmar arch. The external division 

 supplies the Abductor pollicis. Opponens pollicis. ami superficial head ^\ the 

 Flexor brevis pollicis. and occasionally the deep head of that muscle. The 

 other muscles of the thumb are supplied by the ulnar. It then divides into 

 first, second, and third digital branches for the thumb and index finger. The 

 internal division gives off the fourth and fifth digital branches which supply the 

 contiguous sides of the index and middle fingers and the middle ami ring fi] 

 then there are five digital branches from the median nerve. 



