314 ANATOMY OF VERTEBRATES. 



This distributes a ' circumflex ' or axillary, an ulnar, a radial or 

 ' musculo-spiral,' and a median nerve. The circumflex supplies 

 the latisshnus dorsi, clavieulo-brachialis, supercoracoideus and 

 teres minor, and terminates on the integument at the back of the 

 arm. The ulnar nerve divides at the upper third of the humerus 

 into a branch supplying the extensor communis digitorum, ex- 

 tensor proprius pollicis, and ulnaris externus, a branch for the 

 triceps brachii, and a superficial cutaneous nerve distributed to 

 the integument on the back of the fore-arm and hand. The 

 radial nerve passes to the outer side of the humerus, distributing 

 muscular branches in its course, winds to the inner side, descends 

 in front of the elbow-joint, and terminates in muscular and 

 cutaneous branches. The median nerve passes along the back- 

 part of the scapula, giving branches to the pectoralis major, to 

 the shoulder-joint and surrounding skin : passes between the 

 humeral tuberosities, supplying the triceps brachii and brachialis 

 internus : then divides into an external branch, passing between 

 the pronator teres and radialis internus, and supplying the flexors 

 of the digits, and into an internal branch, gliding between the 

 radius and ulna, and ultimately forming the volar arch. 



In the Frog the axillary nerve sends a branch to the muscles 

 and skin above the scapula: it is continued into the brachial, 

 which bifurcates. One branch winds round the humerus, like the 

 ' musculo-spiral,' sends a branch to the extensor cubiti, and passing 

 in front of the elbow-joint penetrates the mass of flexor muscles, 

 and reappears at the outer side of the fore-arm : it sends one 

 branch to the skin, and another to the back of the hand, which 

 divides to supply the same aspect of the digits. The other 

 division of the brachial nerve represents the ' median ; ' it divides 

 into a larger branch, running along the interosseous furrow of the 

 ulno-radial bone, which supplies the palm and palmar surface of 

 the digits, and into a smaller branch, which supplies the flexor 

 muscles of the digits. 



The spinal nerves of the Serpent differ from those of the Eel 

 in the more distinct ganglion on the posterior root, and this rises 

 closer to the anterior root, which is rather larger. Each spinal 

 nerve communicates with the sympathetic, and accompanies 

 the rib, to be distributed to the vertebral muscles and integu- 

 ment, fig. 206. 



In the Tortoise, nerves, analogous to the phrenic, are sent from 

 the first three dorsal pairs to the sheets of the diaphragmaticus, 

 fig. 150, 42. Succeeding dorsal nerves communicate with the 

 sympathetic, and send filaments into the substance of the carapace, 



