THE NERVES 141 



The posterior deep pectoral is usually supplied by two nerves, one 

 of which is derived from the posterior root of the median and is distri- 

 buted to the anterior portion of the muscle. The other is given off 

 with the subcutaneous thoracic nerve, and runs to the posterior portion 

 of the muscle. 



The Nerve to the Latissimus Dorsi 



This nerve passes backwards from the plexus across the subscapularis 

 and teres major muscles to reach the muscles which it supplies. The 

 eighth cervical and the dorsal roots of the plexus supply the fibres of 

 this nerve. 



The Nerve to the Teres Major 



This nerve has a common origin from the plexus with the circumflex 

 nerve. It takes a course downwards and backwards, crossing the sub- 

 scapularis muscle and the branch of the subscapular artery which runs 

 along the glenoid border of the scapula, to reach the teres major muscle 

 which it supplies. 



The Subscapular Nerves 



There are usually two of these, and their fibres come from the cervical 

 roots of the plexus. They split up into a number of short filaments 

 which enter the subscapularis muscle. 



The Circumflex Nerve 



This is sometimes called the axillary nerve. It is a nerve of con- 

 siderable size, and its fibres are derived from the sixth (occasionally), 

 seventh, and eighth cervical roots of the plexus. 



It takes a course downwards and backwards on the subscapularis 

 muscle to the line of apposition of this muscle and the teres major. 



