288 ABRAM T. KERR 



DISTRIBUTION OF THE MATERIAL USED AS TO SEX, COLOR AND 



SIDE OF THE BODY 



It has been possible to divide the plexuses into certain groups 

 and an attempt has been made to determine if one variety of 

 plexus occurs more frequently in white or in colored subjects, 

 in the male or in the female sex, and upon the right or the left 

 side of the body. As the 175 plexuses which were found satis- 

 factory were selected wholly with regard to the accuracy of the 

 record it is at once clear that there would not be an equal number 

 of male and female, white and colored, right and left plexuses. 

 In order to be able to determine the percentage of frequency of 

 each type of plexus among the sexes, the colors, and the sides 

 of the body, it is necessary first to classify the material used. 



Table V shows how irregular this distribution is. It will be 

 seen that 1 14 of the 175 plexuses or 65.14 per cent are from males, 

 while there are only 61 or 34.85 per cent from females. That is, 

 there are only slightly more than half as many from females as 

 from males. 



Of the 114 plexuses from males, 65 are from white and 49 

 from colored subjects and of the 61 plexuses from females, 20 

 are from white and 41 from colored subjects. That is, the num- 

 ber from white males is slightly greater than the number from 

 colored males, while there are more than twice as many plexuses 

 from colored as from w^hite females. In spite of this, because 

 of the large proportion of white males, the total number of plex- 

 uses from colored subjects (90) is only slightly more than the total 

 number from white subjects (85). 



Taking each sex separately or both combined, the plexuses 

 will be seen to be distributed nearly equally on the two sides of 

 the body. This is quite independent of the total number of 

 bodies, since, as already noted, the records from both sides of 

 all of the bodies are not included in the series. 



SPINAL NERVES FORMING THE BRACHIAL PLEXUS 



All anatomists are agreed that, in man, the anterior rami 

 (ventral primary divisions) of the caudal four cervical nerves 



1 For tables see pp. 376-380. 



