DERMATOGLYPHICS IN PRIMATES 15 



deviation 6.7, and the coefficient of variation, 12.0. It will be 

 evident, therefore, that notwithstanding the existence of finer 

 ridges in the chimpanzee palm, the magnitudes of variation in 

 the relation of hand length and ridge count are equivalent 

 in man and chimpanzee. It will be recalled that the series of 

 200 human subjects is made up of young adults. The chim- 

 panzee material comprises both adults and juveniles, indi- 

 cating that the comparisons with man should be carried 

 further to include a comparable group of human subjects. 

 Such a group is available in the series of twenty individuals 

 originally reported in the chimpanzee study. The indices 

 here range from 51 to 126, the mean being 77.6. The standard 

 deviation is 9.9 and the coefficient of variation 12.8. The 

 variability is thus equal to that in the human series composed 

 wholly of adults as well as to the chimpanzee material com- 

 prising both adults and juveniles. 



In the collective primate series the index presents a much 

 wider range, 17 to 112. 1 While the mean, 51.5, is not signifi- 

 cantly smaller than that of the chimpanzee series, the varia- 

 bility is much more pronounced (standard deviation, 28.7; 

 coefficient of variation, 55.7). These findings show that varia- 

 bility among genera, with respect to the proportion of hand 

 length and ridge count per centimeter, is far greater than 

 the variability within a genus or species. 



It is possible that variations in breadths of epidermal 

 ridges, both absolute and relative to hand length, would 

 throw light on the problem of ridge function if the variations 

 were carefully collated with differing habits of the animals. 

 Apparently significant is the fact that the range of variation 

 in absolute ridge breadth is quite limited, in spite of large 

 differences among the genera in hand length and body size. 

 This confined range of variability in the breadths of epidermal 



1 The upper limit of the hand length/ridge-count indices is raised slightly by 

 the recent addition of four adult orangs, in which the average index is 117. The 

 actual values are: 21.7/21.5 = 101; 24.4/22.5 = 108; 24.3/21.5 = 113; 25.0/17.0 

 = 147. These results are not included in the statistical analysis of ridge breadth, 

 but it may be noted that the finding in Pongo is in keeping with the generalizations 

 stated in this section. 



