6 THE ANATOMY OF THE HOESB. 



flat fasciculus giving off the subscapular, etc. ; 2. to join the cord from which arise the 

 posterior root of the median, the ulnar, and the subcutaneous thoracic nerve ; 3. to tlie 

 anterior root of the median and the nerve for the anterior deep pectoral muscle. 



IV. The roots from the 1st and 2nd dorsal nerves unite to form a common cord which 

 divides its fibres in two directions, viz.,— 1. To join the aiove-mentioned cord giving off 

 the posterior root of the median, etc. ; 2. to join the broad fasciculus from which arise 

 the subscapular, etc. 



The following is a list of the branches of -the plexus : — 



1. The phrenic or diaphragmatic nerve (in part). 



2. The suprascapular nerve. 



3. Nerves to the pectoral muscles. 



4. The nerve to the subscapulars. 



5. Nerves to the serratus magnus and levator scapulte (cervical 



portion of the serratus), the latter only in part. 



6. The circumflex nerve. 



7. Nerves to the teres major and latissimus dorsi. 



8. The musoulo-spiral nerve. 



9. The median nerve (two roots). 



10. The ulnar nerve. 



11. The subcutaneous thoracic nerve. 



The Phbenio Neevb. This nerve is formed by the union of two, or 

 sometimes three, branches. The inconstant branch comes from the 

 5th cervical; the other two come from the 6th and 7th respectively. 

 The root from the 6th nerve gives off a branch to the brachial plexus, 

 and then imites on the scalenus with the root from the 5th — when that 

 is present. The single cord resulting passes obliquely backwards and 

 downwards, and at the lower edge of the scalenus it joins with the root 

 from the 7th nerve. This last comes from the fore part of the brachial 

 plexus. The trunk of the nerve, as thus formed, passes backwards 

 between the axillary artery and its inferior cervical branch, and enters 

 the thorax. It is the motor nerve to the diaphragm. 



The Nerves to the Levator Anguli Scapula and Rhomboid etjs. 

 In Plate 3 two nerves are seen at the upper edge of the scalenus. 

 They are not, strictly speaking, branches of the brachial plexus ; 

 but come from the inferior primary branch of the 6th nerve, and 

 pierce the muscle either together or separately. They are distributed 

 to the levator anguli scapulse, and the posterior of the two is continued 

 in that muscle to reach the rhomboideus. 



The Nerve to the Sbeeatus Magnus is formed by the union of two 

 branches, which pierce the upper division of the scalenus before uniting. 

 These are branches of the 7th and 8th nerves respectively. By their 

 fusion there is formed a broad nerve, which passes backwards on the 

 surface of the serratus, distributing its filaments upwards and downwards. 

 Before fusion, the branch from the 7th gives off a nerve which is 

 distributed to both the levator and the serratus. 



