568 SPINAL NERYES. 



The Communicating branch with the phrenic is derived from the fifth cervical 

 nerve ; it joins the phrenic on the Anterior scalenus muscle. 



The Muscular branches supply the Longus colli, Scaleni, Khomboidei, and 

 Subclavius muscles. Those for the Scaleni and Longus colli arise from the lower 

 cervical nerves at their exit from the intervertebral foramina. The rhomboid branch 

 arises from the fifth cervical, pierces the Scalenus medius, and passes beneath the 

 Levator anguli scapula?, which it occasionally supplies, to the Ehomboid muscles. 

 The subclavian branch is a small filament, which arises from the trunk formed by 

 the junction of the fifth and sixth cervical nerves ; it descends in front of the 

 subclavian artery to the Subclavius muscle, and is usually connected by a filament 

 with the phrenic nerve. 



The Posterior thoracic nerve (long thoracic, external respiratory of Bell) 

 supplies the Serratus magnus, and is remarkable for the length of its course. It 

 arises by two roots, from the fifth and sixth cervical nerves, immediately 'after 

 their exit from the intervertebral foramina. These unite in the substance of the 

 Middle scalenus muscle, and, after emerging from it, the nerve passes down behind 

 the brachial plexus and the axillary vessels, resting on the outer surface of the 

 Serratus magnus. It extends along the side of the chest to the lower border of 

 this muscle, and supplies it with numerous filaments. 



The Suprascapular nerve arises from the cord formed by the fifth, sixth, and 

 seventh cervical nerves ; passing obliquely outwards beneath the Trapezius, it enters 

 the supra-spinous fossa, through the notch in the upper border of the scapula ; 

 and, passing beneath the Supra-spinatus muscle, curves in front of the spine of the 

 scapula to the infra-spinous fossa. In the supra-spinous fossa, it gives off two 

 branches to the Supra-spinatus muscle, and an articular filament to the shoulder- 

 joint ; and in the infra-spinous fossa, it gives off two branches to the Infra-spinatus 

 muscle, besides some filaments to the shoulder-joint and scapula. 



(2.) BRANCHES BELOW THE CLAVICLE. 

 To the chest .... Anterior thoracic. 



To the shoulder \ ^scapular. 



( Circumflex, 

 f Musculo-cutaneous. 

 I Internal cutaneous. 



m ,-, f -, i T ! Lesser internal cutaneous. 



To the arm, forearm and hand -4 Ar -,. 



j Median. 



Ulnar. 

 Musculo-spiral. 



The branches given off below the clavicle are derived from the three cords of 

 the brachial plexus, in the following manner: 



From the outer cord, arise the external of the two anterior thoracic nerves, the 

 musculo-cutaneous nerve, and the outer head of the median. 



From the inner cord, arise the internal of the two anterior thoracic nerves, the 

 internal cutaneous, the lesser internal cutaneous (nerve of Wrisberg), the ulnar, 

 and inner head of the median. 



From the posterior cord, arises the subscapular ; and it then subdivides into the 

 musculo-spiral and circumflex nerves. 



The Anterior Thoracic Nerves, two in number, supply the Pectoral muscles. 



The external or superficial branch, the larger of the two, arises from the outer 

 cord of the brachial plexus, passes inwards, across the axillary artery and vein, 

 and is distributed to the under surface of the Pectoralis major. It sends down a 

 communicating filament to join the internal branch. 



The internal or deep branch arises from the inner cord, and passes upwards 

 between the axillary artery and vein (sometimes perforates the vein), and joins with 

 the filament from the superficial branch. From the loop thus formed, branches 

 are distributed to the under surface of the Pectoralis minor and Poctoralis major 

 muscles. 



