222 ELEMENTS OF MAMMALIAN ANATOMY. 



101): the external cutaneous, the internal cutaneous, 

 the musculospiral, the median, and the ulnar. The 

 external cutaneous arises from the sixth and seventh 

 cervical nerves and passes distad along the caudal aspect 

 of the biceps to the cephalic aspect of the forearm, where 

 it becomes subcutaneous. It supplies the biceps and 

 coracoid muscles and the skin of the forearm. The 

 internal cutaneous arises from the first thoracic and 

 passes along the ventral side of the arm, becoming 

 subcutaneous just proximad of the elbow, where it is 

 distributed to the skin of the arm and forearm on the 

 caudal and ventral aspects. 



The musculospiral arises from the seventh and eighth 

 cervical and first thoracic nerves. It is the largest 

 component of the brachial plexus. It winds obliquely 

 around the humerus to the cephalic aspect, where it 

 divides into two branches, the radial and the posterior 

 interosseous. The radial nerve is the smaller and be- 

 comes subcutaneous near the elbow, and passes along 

 the radial region. The posterior interosseous proceeds 

 along the dorsal aspect of the forearm to the wrist, 

 where it divides into branches supplying the digits. 



The median nerve arises from the seventh and eighth 

 cervical and first thoracic. It follows the course of 

 the brachial artery, passing through the supracondylar 

 foramen to the elbow, where it passes beneath the pro- 

 nator teres to the carpal region, and supplies the first, 

 second, and third digits. It also supplies the pronator 

 teres and flexor muscles of the forearm. 



The ulnar nerve (Fig. 101) is derived from the eighth 

 cervical and first thoracic. It courses with the brachial 

 artery to the middle of the humerus, where it turns 

 caudad to pass between the olecranon process and 

 internal condyle of the humerus. It is here sub- 



