STUDIES IN HUMAN HEREDITY 297 



its history. The left-handed condition of the boys is attributed to the influ- 

 ence of a left-handed nurse. Left-handed nurses are frequently held respon- 

 sible for the left-handedness of their charges. I have many such com- 

 plaints. Possibly in some cases of acquired left-handedness this occurs. 

 But usually if careful search is made left-handedness or ambidexterity 

 appears somewhere in the pedigree. In contradiction of the potency of a 

 left-handed nurse's influence is the case given in chart, figure 25, in which 

 among a fraternity of ten, \viih left-handed predigree, all having had the 

 same left-handed nurse, only one is left-handed. 



The succeeding sixteen pedigrees (6 to 21) are of children of six Vir- 

 ginia public schools, kindly secured for me by the respective teachers. 

 The six schools comprised ninety-four (94) females and seventy-two (72) 

 males including three (3) left-handed females and ten (10) left-handed 

 males. Thus among one hundred and sixty-six (166) school children there 

 are thirteen (13) left-handed individuals or about 8 per cent, an abnormally 

 high proportion. A school at Gainesville, Florida, has two hundred and 

 four (204) females and one hundred and ninety (190) males, among whom 

 are one (1) left-handed female and five (5) left-handed males. The pro- 

 portion here is somewhat less than 2 per cent, which is about normal. In 

 both instances, however, the total number is too small to furnish informa- 

 tion of much value respecting actual percentages. The preponderance of 

 left-handed boys over girls is very strildng. In my earlier work on left- 

 handedness, representing a much larger canvass, the number of left-handed 

 whites in the school population was 2 per cent, of blacks 4 per cent; and the 

 number of left-handed males and females was approximately equal in both 



a 



•~rO 



■a 



6 



4466666 



Fig. 6. 



Charts like number 6 indicate that in the matter of dexterity* we are 

 dealing with grades corresponding to degrees of dominance. If right-hand- 



* i.e., use of hand. 



