12 CHARLES MIDLO AND HAROLD CUMMINS 



the same genus. At present it is not even certain that epi- 

 dermal ridges can be justly regarded as having a uniform 

 functional service in all mammals which possess them. 



RIDGE BREADTH 



It is obvious, since ridges participate in the growth of the 

 hand and foot, that determinations of generic characteristics 

 of ridge breadth and comparisons of genera can not be made 

 unless the material is standardized according to growth stages. 

 Schlaginhaufen presents determinations of ridge breadth in 

 several primates, but because he failed to indicate the growth 

 status of all the animals, we introduce some comparative 

 results obtained without exception from adults. Even in the 

 case of man, information bearing on variation in ridge breadth 

 is scanty. Cummins, Waits and McQuitty ('41) have investi- 

 gated individual and regional variation in ridge breadth of 

 the human hand. These authors obtain an indirect measure 

 of ridge breadth by counting the number of ridges transected 

 at right angles by a line of 1 cm. In the present determinations 

 the same method is followed, though the observations are 

 limited to a single region in the palm, the proximal portion 

 of the hypothenar area (H p as denned below). This area is 

 found to be the most favorable for orienting the line of count 

 at right angles to the ridges, and moreover it is an area which 

 in the available material is consistently clearly imprinted. 

 For the comparison, thirteen animals representing eleven 

 genera are available in actual prints, as listed in table 2, and 

 one human hand is added for completion of the series. With 

 the limitation of numbers of individuals nothing can be done 

 with the question of individual variation; our primary 

 emphasis is on the absolute ridge count per centimeter and 

 its relation to hand size. It has been shown by Cummins, Waits 

 and McQuitty that in the human hand there is a slight negative 

 correlation (0.30 0.05) between ridge count and hand 

 length. It might thus be expected that there would be evi- 

 denced among the genera an inverse relationship between 

 ridge counts per centimeter and hand lengths. A loose rela- 



