BRACHIAL PLEXUS. 



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distrlbated to the back of the neck, and are very small. Their 

 Anterior Branches are principally appropriated to the upper 

 extremities, and are very large. They generally send each a 

 small twig to the lower cervical ganglion of the intercostal 

 nerve, and a few small branches to some 

 of the contiguous muscles. They are 

 arranged and combined so as to form the 

 net- work, now to be described, which is 

 called the Brachial or Axillary plexus ; 

 and, in the formation of this plexus, they 

 are joined by the anterior branch of the 

 first dorsal nerve. 



The Brachial Plexus 



Extends from the lower part of the 

 side of the neck into the arm-pit. It 

 commences in the following manner. The 

 fourth and fifth cervical nerves proceed 

 downwards, and after uniting to each other 

 about an inch and a half below their 

 egress from the spine, they separate again, 

 almost immediately, into two branches. 



The sixth cervical nerve, after passing 

 downwards, divides also into two branches, 

 one of which unites with the upper-, 

 most branch that proceeds from the union 

 of the fourth and fifth, and the other 

 with the lowermost, and they all proceed 

 downwards. 



* The Brachial plexus of nerves with its branches and their distribution. 1. 

 The brachial plexus. 2. The short thoracic nerves. 3. The long thoracic or 

 external respiratory of Bell. 4. The phrenic nerve. 5. The supra-scapular 

 nerve. 6. The subscapular nerves. 7. The external cutaneous nerve. 8. 

 The point at which it pierces the deep fascia. 10. The origin of tlie median 

 nerve by two heads. 11. The bend of the elbow where the median passes be- 

 tween the two heads of the pronator radii teres, and of the flexor sublimis digi- 

 torum. 12. Its muscular branches. 13. Its anterior interosseous branch. 14. 

 The point at which the nerve passes beneath the annular ligament, and divides 

 into six terminal branches. The branch which crosses the annular ligament is 



