298 ABRAM T. KERR 



females by 12.(59 per cent in group 2, and the percentage from 

 white males exceeds the percentage from white females by .77 

 per cent in group 3. It must be remembered also that the 

 extreme variation is but a few per cent. 



Plexuses of group 2 occur more often on the right side and 

 groups 1 and 3 on the left. Since there is a more or less gradual 

 change from a cephalic to a caudal position in passing from group 

 1 to group 3 it is difficult to attach any significance to the fact 

 that group 1 occurs 1.57 per cent more often on the left side, group 

 2, 4.91 per cent more often on the right, and group 3, 3.35 per 

 cent more often on the left. 



Whether the form of the plexus is influenced by or influences 

 right and left handedness it was impossible to tell as there was 

 no record as to whether the subjects had been -right or left 

 handed. It is altogether improbable that so large a proportion 

 more than half were left handed. 



Plexuses of groups 1 and 3 occur more often in white and of 

 group 2 in colored subjects. We have here the same conditions 

 as for the two sides of the body only here the percentage of 

 difference is greater. The difference in percentage in favor of 

 the white is 5.89 per cent in group 1, and 3.86 per cent in group 3; 

 while it is 9.74 per cent in favor of the colored in group 2. 



I ani' quite convinced that so far as this investigation has been 

 carried it does not sho\V that sex, color or side of the body has 

 any influence whatever in determining the group of plexus. 



It will be noted that in many of these subdivisions but a small 

 number of cases are-considered and that the percentages of varia- 

 tion are in no case great. It would seem not at all improbable 

 that if a greater number of cases were considered equally dis- 

 tributed among the sexes, colors, sides, etc., that the irregularity 

 in this particular would be much less marked. 



CEPHALIC AND CAUDAL POSITION OF THE PLEXUS 



Various authors have classified the brachial plexus as cephalic 

 and caudal, high and low, or prefixed and postfixed, meaning b}- 

 this a i)osition or strength of the plexus nearer to or farther from 

 the head end of the body. The classifications are usually based 



