STUDIES IN HUMAN HEREDITY 303 



ous). The appearance of left-handed uncles indicates inheritance, but the 

 manner or scheme is obscure. Chart, figure 19, belongs to the same 

 obscure category; but here again there are left-handed collaterals,* two 

 first cousins of the mother. Chart, figure 20, again can be explained in 

 terms of heredity only by making the probable assumption that the parents 

 are heterozygous. The boy of this childship writes with the left hand. 

 Chart, figure 21, must be similarly interpreted. 



Viewang the pedigree charts as a whole there seems to be too much 

 left-handedness on the assumption that that character is recessive. It 

 must be remembered, however, that the childships are mostly small, and 

 the pedigrees relatively restricted. When a certain character is under 

 investigation, naturally for the most part, only those families come to be 

 included in which children show the characters. The small normal frater- 

 nities of affected parents fail of inclusion, although they should be included 

 for accurate percentages and proper testing of hereditary hypotheses. It is 

 a striking fact that the larger the fraternities and the more extensive the 

 pedigrees the more of a recessive nature does the pathologic character 

 assume. The extensive pedigrees of the Davenportsf indicate that human 

 albinism is a recessive character; earlier much smaller pedigrees seemed to 

 indicate that it was dominant. When more extensive pedigrees of other' 

 pathologic characters, which now appear to partake of the nature of domi- 

 . nance, are known, they too maj^ be found to be Mendelian recessives. 

 The eugenic significance of the point is of the utmost import. 



In a recent work on left-handedness in certain gramineae — including 

 two- and six-rowed barley, oats, millet, rye and maize where the character 

 is shown to be not hereditary — R. H. Comptont calls attention in a foot- 

 note to a pedigree recorded by Cunningham, § cited from Aim^ P6r6;^ 

 which seems to disprove my assumption that right-handedness behaves in 

 heredity as a dominant. It must be admitted that there are a small num- 

 ber of cases which indicate that left-handedness is the dominant character 

 e.g., figures 12 and 14. And this may indeed be the fact in certain human 

 strains. Here we must postulate a condition of reversed dominance. 

 P6r^ gives two interesting cases. In one both parents were left-handed; 

 of their five children, four were left-handed. This case so closely accords 

 with expectation (total) on Mendelian principles, that the single probable 

 exception among five individuals is not really subversive of the general 



* Not shown in chart. 



t Am. Nat., 44: 527 and 528. 



J Journal of Genetics, 2: 1, 1912. 



§ lac. cit. 



^ Les courbures laterales normales du rachis humain, Toulouse, 1900. 



