BRACHIAL PLEXUS OF NERVES IN MAN 291 



There is another group of plexuses in which the whole of the 

 fifth cervical nerve enters the plexus without any additions from 

 the fourth cervical. This type has been called group 2. There 

 are 52 records or 29.71 per cent of the cases in group 2. 



There is a third group of plexuses, to be known as group 3, 

 in which not only does no part of the fourth cervical nerve enter 

 the plexus but also the plexus does not receive the whole of the 

 fifth cervical nerve. A portion of the fifth cervical joins with 

 the fourth to aid in the formation of the cervical plexus. There 

 are 13 plexuses or 7.42 per cent of the cases in group 3. 



In round numbers we find then that in over 62 per cent of the 

 cases the fourth cervical nerve sends a branch to the brachial 

 plexus and in about 37 per cent it does not. That in this latter 

 case the whole of the fifth cervical nerve enters the plexus in 

 nearly 30 per cent of the cases and only part of the fifth cervical 

 contributes in over 7 per cent. 



The three groups into which the plexuses have been divided 

 may be briefly described as follows: 



Group 1, in which a part of the fourth cervical nerve enters 

 the plexus, and containing 62.85 per cent of the plexuses (fig. P) ; 



Group 2, in which the fourth cervical nerve does not enter the 

 plexus but the whole of the fifth cervical nerve does, and con- 

 taining 29.71 per cent of the plexuses (fig. 2); 



Group 3, in which onl}^ a part of the fifth cervical nerve joins 

 the plexus, and consisting of only 7.42 per cent of the cases 



(fig. 3). 



Group one 



From table 2, it will be observed that 70 of the 110 plexuses in 

 group 1 are from males and 40 of them from females, or 63.63 

 per cent of the group are from males and 36.36 per cent are from 

 females. There are, however, only 61 plexuses from females 

 while there are 114 from males, table 1. Forty of the 61 plexuses 

 from females are found in group 1, or 65.57 per cent of the 

 female plexuses, table 6. Seventy of the 114 plexuses from 

 males are found in this group, or 61.40 per cent of the male 



3 For figures see pp. 381-395. 



