NERVOUS SYSTEM. 115 



CERVICAL NERVES. 



Eight in number. Divided into superior branches which 

 anastomose freely, forming the deep cervical plexus, and send fila- 

 ments to muscles, nerves and integument of sides and top of 

 neck. The inferior branches supply the structures on the under 

 side of the neck, forming the superficial cervical plexus, and the 

 sixth, seventh and eighth form a portion of the brachial plexus. 



Branches. 



Phrenic nerves, from the fifth and sixth cervical, and branch 

 from the brachial plexus, pass down inside thorax to front of 

 diaphragm, which they supply. 



BRACHIAL PLEXUS. 



A large fasciculus of nerves which supply the anterior limb and 

 anterior portion of the chest and neck. 



Formation. By inferior branches of sixth, seventh, and eighth 

 cervical and first two dorsal nerves, which unite and subdivide 

 opposite the scapulo-humeral joint into branches to the thorax 

 and anterior extremity. 



Branches. 



Muscular, to angularis scapula, rhomboideus, latissimus dorsi, 

 teres major, subscapularis . 



Superior thoracic (or external respiratory of Bell), to serratus 

 magnus. 



Pectoral or inferior thoracic, to superficial and deep pectorals. 



Subcutaneous thoracic, follows spur vein and supplies pannicu- 

 lus carnosus and subcutaneous muscles of neck. 



Circumflex, to abductors of limb, teres major, levator humeri, 

 shoulder-joint and integument about shoulder. 



Super-scapular, from sixth and seventh cervical to antea- and 

 postea-spinati. 



Musculo-cutaneous, from seventh and eighth, crosses axillary 

 artery, passes down front of arm between two insertions of coraco- 

 humeralis, supplying it and the coraco-radialis. 



Radial (largest branch of plexus), passes down parallel with 

 humeral artery, follows short flexor of forearm and radial artery to 

 oblique extensor of metacarpus. 



