THE BEACHIAL PLEXUS. 



passes backwards, and is expended in the skin of Fig. 354. 



the back, and inner part of the fore-arm. 



2. The musculo-cutaneous or perforans casserii, 

 whose disposition is analogous to that of Carnivora. 



3. The axillary nerve, regarding which there is 

 nothing to say. 



4. The radial nerve (musculo-spirdl) passes as in 

 animals, lies in the twisted furrow of the humeru?, 

 gives off an internal and external cutaneous branch, 

 and reaches the antero-external part of the arm, in 

 the space between the anterior brachial and long 

 supinator, where it terminates by two branches. 

 The anterior of these reaches the back of the hand, 

 and gives off three ramuscules there, which are dis- 

 tributed as follows: the first forms the external 

 dorsal collateral of the thumb ; the second bifur- 

 cates, and constitutes the internal dortal collateral 

 of the thumb and external collateral of the index ; 

 lastly, the third supplies the internal collateral of 

 the index and external of the medius. This branch 

 always anastomoses with the dorsal branch of the 

 ulnar. The posterior branch, motor, is expended in 

 the muscles on the posterior and external aspect of 

 the fore-arm. 



5. The median nerve commences by two branches : 

 one arises in common with the musculo-cutaneous 

 or anterior brachial, and corresponds to the anasto- 

 mosis found around the axillary artery of the Horse ; 

 the other is detached from the trunk common to the 

 ulnar and internal cutaneous. The median runs 

 along the biceps, passes in front of the elbow, and 

 lies beneath the annular ligament of the carpus, 

 where it terminates in furnishing : 1, A filament to 

 the short abductor of the thumb ; 2, Palmar ramus- 

 cules to the thumb, index, and medius, and external 

 border of the annularis. This disposition of the 

 medius, therefore, much resembles that of the Cat. 



6. The ulnar nerve passes along the inner border 

 of the arm and fore-arm, and divides, a little above 

 the inferior extremity of the olecranon, into two 

 terminal branches a dorsal and palmar. The first 

 is directed on the back of the hand, and separates 

 into three metacarpal branches, which, in their course, 

 furnish the dorsal collaterals of the auricularis and 

 annularis, and internal collateral of the medius ; the 

 other parts of the hand are supplied by the radial. 

 The second, or palmar branch, is superficial, and 



detaches the palmar collaterals of the little ringer NERVES OF THE FRONT OF FORE- 

 and internal collateral of the annularis, as well as ARM AND HAND OF MAN. 



a deep ramuscule that lies across the interosseous i Supinator longus, cut 2, Ulnar 

 muscles, and is a motor nerve. To resume, we see nerve; 3, Brachialis anticus; 4, 

 that this distribution of the terminal branches of Biceps; 5, Musculo-spiral nerve, 

 the brachial plexus of Man much resembles that Q Median nerve 7 Posterior 

 described in Carnivora, and especially in the Cat. interosseous nerve', 8, Pronator 



teres and flexor carpi radialis, cut j 

 9, Extensor carpi radialis longior, 



cut ; 10, Brachial artery ; 11, Supinator brevis ; 12, Flexor sublimis digitorum, cut , 

 13, 13, Radial nerve ; 14, 14, Flexor carpi ulnaris , 15, Extensor carpi radialis brevior , 

 16, Ulnar artery ; 17, Radial origin of flexor sublimis digitorum, cut ; 18, Flexor pro- 

 fundus digitorum; 19, Tendon of pronator teres; 20, 20, Dorsal branch of ulnar 

 nerve; 21, 21, Radial artery; 22, 22, Deep branch of ulnar nerve; 23, Flexor longus 

 pollicis; 24, Abductor minimi digiti ; 25, Anterior interosseous nerve; 26, Digital 

 branches of ulnar nerve ; 27, Tendon of supinator longus ; 28, One of the lumbricalcs 

 muscles; 29, Pronator quadratus; 31, Tendon of flexor carpi radialis; 33, Digital 

 branches of median nerve ; 35, Adductor pollicis. 



