THE NERVOUS SYSTEM. 221 



about two centimeters from their origin (Fig. 47). The 

 manner in which the nerves anastomose varies some- 

 what, but the following will be found approximately 

 correct : 



The sixth cervical nerve gives off a small branch to 

 the rhomboideus and levator anguli muscles of the 

 shoulder, and then divides into two nearly equal 

 branches, one of which supplies the muscles on the 

 lateral aspect of the scapula, and the other joins with 

 the seventh cervical nerve. Small branches from the 

 fifth and sixth cervical nerves unite to form the phrenic 

 nerve supplying the diaphragm. 



The seventh cervical nerve gives off three small 

 branches at about the same point, one of which is the 

 ..posterior thoracic supplying the serratus magnus muscle, 

 a second helps to form the musculocutaneous, and the 

 third forms part of the median and anterior thoracic. 

 The main portion of the seventh cervical unites with the 

 eighth and first thoracic, to form the musculospiral nerve. 

 The circumflex and subscapular branches supplying the 

 deltoid and subscapular muscles are also derived from the 

 seventh. 



The eighth cervical nerve, after giving off a small 

 branch to the pectoral muscle, a small twig to the median 

 nerve, and a large branch to the first thoracic nerve, 

 is continued as the main part of the musculospiral nerve. 



The first thoracic nerve gives first a large branch 

 to the musculospiral nerve, a second small branch to 

 the anterior thoracic, and a third branch forming the 

 internal cutaneous nerve supplying the skin of the arm 

 and forearm on the caudal aspect. The main portion 

 of the first thoracic nerve then continues as the main part 

 of the ulnar nerve. 



The nerves of the forelimb are five in number (Fig. 



