BRACHIAL PLEXUS OF NERVES IN MAN 297 



two ways: first, within the group, that is, by comparing the 

 number of plexuses in the group from white, colored, male and 

 female, right or left, with the total number of plexuses in the 

 group; secondly, by comparing the number of male plexuses in 

 the group with the total number from males studied and the 

 number from females in the group with the total number from 

 females studied, etc. I consider the latter far the more accurate 

 and shall use that almost entirely in the following comparison 

 of the three groups. 



Although comparing the plexuses of each group separately, 

 because of the great preponderance of plexuses from males, the 

 percentage of the plexuses from this sex greatly exceeds those 

 from females, yet if we take the plexuses from males and females 

 of each group and compare them with the total number of plexuses 

 from males and from females it will be seen that groups 2 and 3 

 occur more often among the males and group 1 among the females. 

 That is, that plexuses in which the fourth cervical nerve enters, 

 plexuses which have the most cephalic origin, occur more often 

 among females than among males. This seems to indicate that 

 the plexus in the female tends to be more cephalic in position 

 than in the male. But we find that the difference in the fre- 

 quency of occurrence of plexuses from males over females in group 

 2 is 2.84 per cent but in group 3 is but 1.34 per cent; while if 

 much of any significance were to be given to the greater frequency 

 of group 1 among females we should expect to find them least 

 frequent in group 3, the most caudal group, and not in group 2 

 intermediate, which happens to be the case. 



Furthermore, if we take the plexuses from colored and white 

 males and females of each group and compare them with the 

 total number of colored and white males and females respectively, 

 we find that in group 1 the percentage of colored males is 1.79 

 less than the percentage of colored females; in group 2, 0.55 

 per cent more colored males than females; and in group 3, 1.25 

 per cent more colored males than females. On the other hand 

 the percentage of plexuses from white females exceeds the per- 

 centage from white males by 11.93 per cent in group 1; the 

 percentage from white males exceeds the percentage from white 



