BRACHIAL PLEXUS OF NERVES IN MAN 289 



and a part of the first thoracic nerve^ always enter into the 

 formation of the brachial plexus. There is more or less vague- 

 ness, however, as to the frequency with which one or both of the 

 nerves adjoining these nerves cephalad and caudad also send 

 branches to the plexus. Thus different authors state that there 

 is 'sometimes' a fasciculus from the fourth cervical to join the 

 plexus or that 'frequently,' or 'in many cases' or 'usually' such a 

 branch is present, and similarly that a filament from the second 

 thoracic nerve is found, 'sometimes,' 'frequently,' 'usually,' 

 'in many cases,' or 'not rarely.' In other words, all are agreed 

 that the anterior rami of at least five spinal nerves enter into the 

 formation of the plexus in all cases, but they are not at all clear 

 as to how frequently there may be six or possibly seven nerves 

 entering the plexus. 



In this report, the cephalic limits of the plexus are noted in all 

 instances. The records of the caudal limits are, however, not 

 included, as it was possible to obtain satisfactory records in so 

 few cases that it was thought best to exclude these entirely from 

 •the main statistical tables. In some cases the records of the cau- 

 dal limits of the plexus were not obtained because the second 

 thoracic nerve can only be exposed when the thorax is opened 

 and in many instances this was dissected by a different student 

 than the dissector of the upper extremity. In other cases the 

 nerves were surrounded by strong parietal pleuritic adhesions or 

 were embedded in the shellac mass used for injecting the blood 

 vessels so that it was not possible to make a satisfactory dis- 

 section. 



Eckhard ('62), Kaufmann ('64), Cunningham ('77), Adolphi 

 ('98) and others have shown that the second thoracic nerve, at 

 times contributes to the brachial plexus. Cunningham found 

 the second thoracic nerve joining the first in 27 out of 37 cases. 

 He says, "Sometimes the connecting twig was very large, some- 

 times very fine and seen with difficulty. It may be single, double 

 or triple. When double, usually one twig joins the intercostal 



2 For the sake of brevity, the terms fourth cervical nerve, fifth cervical nerve, 

 etc., will be used in most cases instead of anterior ramus of the fourth cervical 

 nerve, etc. 



