336 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



The chief nerves from the brachial plexus are the following: 

 i. The phrenic nerve. This was described above. 



2. The suprascapular nerve. This is the most anterior nerve arising from 

 the sixth cervical. The main part of this nerve passes between the supraspinal 

 and subscapular muscles to supply the supraspinatus and infraspinatus. In 

 the cat a branch of this nerve passes over the shoulder to more superficial parts. 



3. The ventral thoracic nerves. These nerves supply the pectoral muscles 

 and will be found entering the inner surface of these muscles between the two 

 incisions made above. ' They are the most ventral of the nerves of the plexus. 

 There are two of these nerves— one arising from the seventh cervical, the other 

 from the eighth cervical and first thoracic. The former is small in the rabbit. 



4. The subscapular nerves. There are three of these, dorsally situated and 

 passing into the inner surface of the shoulder. The first. arises from the sixth 

 cervical and passes to the subscapular muscle; the second arises from the seventh 

 cervical and supplies chiefly teres major; the third comes from the seventh and 

 eighth cervicals and runs posteriorly along the internal surface of the latissimus 

 dorsi muscle. 



5. The axillary nerve. This nerve originates chiefly from the seventh cervical. 

 It passes through the upper part of the upper arm, ventral to the triceps and 

 emerging on the lateral surface of the upper arm supplies chiefly the deltoid 

 muscles. 



6. The dorsal or long thoracic nerve. This nerve is best located by examin- 

 ing the outer surface of the serratus ventralis muscle. On tracing it anteriorly 

 the nerve will be found to pass internal to the scalenes and to spring from the 

 seventh cervical nerve close to the vertebral column. 



7. The musculocutaneous nerve (cat only). This arises from the ventral 

 surface of the sixth and seventh cervicals. It passes to the biceps muscle, fork- 

 ing as it approaches the muscle. The posterior branch continues along the 

 surface of the muscle and at the elbow passes to the lateral surface of the arm 

 and supplies the skin of the forearm. 



8. The radial nerve. This is the largest nerve springing from the plexus. 

 Seventh and eighth cervicals and first thoracic nerves contribute to its formation. 

 It passes to the upper arm and coursing between the humerus and the triceps 

 turns distally. It supplies many muscles of the fore limb. 



9. The median nerve. This nerve lies posterior to the radial. It arises in. 

 the cat by branches from the last three nerves of the plexus and in the rabbit 

 chiefly from the first thoracic. It passes to the upper arm, and then 'turns 

 distally running along with the brachial artery. 



10. The ulnar nerve. This lies just posterior and parallel to the median 

 nerve, originating chiefly from the first thoracic nerve. The ulnar and me- 

 dian nerves supply the limb distal to the elbow, although in the rabbit, the 

 median nerve innervates the biceps. 



