156 



THE BIOLOGY OF TWINS 



discussion of his (Wilder's) conclusions appears in the 

 last few pages of this chapter. 



Wilder^ s studies of friction- skin patterns in the palms 

 and soles of twins. — It is a familiar fact that the surest 

 method of identifying human beings is the finger-print 

 method now in use in all modern detective bureaus 

 and prisons. The method is based on the wide range 

 of diversity in the details of the friction-ridge patterns 



'^)> 



Fig. 52. — Photograph (from Wilder) of the left sole-prints of a pair 

 of duplicate twins. The heavy lines are lines of interpretation. Note 

 the striking similarity amounting almost to identity. 



of the palmar surfaces of the hands and feet. No two 

 individuals are exactly alike in all details, but the 

 resemblances between certain types of twins are really 

 surprisingly close. The prints of the left soles of a 

 pair of twins studied by Wilder show identity of general 

 pattern (Fig. 52) but lack of identity in detail, for the 

 exact number of friction ridges in corresponding parts 

 of the pattern differs in the two individuals. 



