176 ANATOMY OF VERTEBRATES. 



to the muscles and skin ; the first dorsal supplies the muscles 

 only. The phrenic nerve is formed by a branch from the fifth 

 and sixth cervicals : it passes over the pericardium to the dia- 

 phragm, and on the right side is placed close to the post-caval 

 vein. In the Jaguar, the phrenic also arises from the fifth and 

 sixth cervicals, and receives a branch from the first thoracic 

 ganglion. The axillary plexus is formed by the last two cervical 

 and first two dorsal nerves. In the Fox the axillary plexus is 

 formed by the sixth and seventh cervical and first and second 

 dorsal nerves, but the greatest part of the sixth, after receiving a 

 branch from the seventh, gives a large branch to the integuments 

 on the anterior part of the shoulder-joint, and then passes to form 

 the superior scapular nerve, and terminates on the supra- and 

 infra-spinate muscles. Branches from the sixth and seventh 

 cervical and first and second dorsals are given to the pectoral 

 muscles ; a branch from the seventh cervical is given to the 

 serratus magnus, and branches from the sixth and seventh go to 

 the subscapularis. The circumflex nerve arises from the union of 

 the sixth and seventh cervical nerves; it gives branches to the 

 subscapularis and teres major muscles, and then divides and sends 

 a branch to the infra-spinatus muscle and the deltoid, and branches 

 to the integuments on the outer side of the arm. 



The internal cutaneous nerve is sent off by the ulnar ; it passes 

 down the arm, and, near the inner condyle of the humerus, divides 

 into branches to be distributed to the skin at the ulnar side of the 

 fore-arm. The smaller internal cutaneous nerve is the external 

 branch of the third dorsal after its egress from between the ribs ; 

 it pierces the broadest muscle of the back, and divides into 

 branches, to be distributed on the skin at the inner and posterior 

 part of the arm. The musculo-cutaneous nerve arises from the 

 seventh cervical with the outer portion of the median, gives a 

 branch to the pectoralis and coraco-brachialis, and then passes off 

 to terminate on the biceps. The seventh cervical, having given 

 off the homologue of the musculo-cutaneous, the remaining part 

 gives off a branch which sends one back to the brachialis interims, 

 behind the tendon of the biceps, and then gives branches to the 

 skin of the fore-arm, in the place of the cutaneous portion of the 

 musculo-cutaneous nerve in Man ; it then joins the branch from 

 the first and second dorsal nerves, about an inch above the elbow, 

 to form the median nerve, which is small as compared with that in 

 Man. The nerve thus formed passes under the origin of the 

 pronator teres, and gives branches to this, the flexor carpi radialis, 

 and the superficial and deep flexors of the digits ; it then passes, 



