Harris Hawthorne Wilder 437 



slightly different external circumstances of nutrition, activity, etc., 

 will develop differences not present at first and not directly connected 

 with the question of the original physical identity. In the study of the 

 epidermic ridges of the ventral surfaces of hands and feet, however, we 

 have an exact field for research, since there is a set of characters here 

 present which are laid down in the embryo and persist until death, 

 beyond the influence of any external change. They are, moreover, actual 

 anatomical parts which can be studied and described, counted and com- 

 pared, and reproduced for illustration by the exact method of printed 

 impressions, a method by which each reader can have the data placed 

 before him as accurately as though he could investigate the objects him- 

 self, and in a much more convenient form. 



Galton, 92 (pp. 185-187), seems to have been the first to make use 

 of these parts in the study of twins, but he confined his examinations to 

 the apical patterns (finger-tips) alone, and although he was one of the 

 first to formulate a scientific distinction between the two types of twins, 

 yet in these investigations he makes no distinction between them, un- 

 doubtedly because in this place his main object was to show their differ- 

 ences and not their similarities. That he then, however, had in mind 

 a more careful biological investigation of exactly this point is shown by 

 the following statement, which is added to the investigations referred 

 to, and which is so exactly the object of a part of the investigation of 

 this paper, that I only hope that my plans, worked out quite inde- 

 pendently, and at first without the knowledge of this statement, may not 

 in any way interfere with anything he may have been preparing. He 

 says : " It may be mentioned that I have an inquiry in view, which has not 

 yet been fairly begun, owing to the want of sufficient data, namely, to deter- 

 mine the minutest biological unit that may he hereditarily transmissible. 

 The minutiae in the finger-prints of twins seem suitable objects for this 

 purpose."^ (The italics are my own.) 



Since Galton, in the work cited, made no direct use of the epidermic 

 markings in the study of duplicate twins as distinguished from the other 

 types, and since he does not seem as yet to have published any investi- 

 gation along the line of his statement quoted above, it appears that I 

 have been the first to actually undertake such an inquiry. In my article 

 "Palms and Soles" (Amer. Jour. Anat., 1902) I have published re- 

 duced tracings (not prints) of the full set of palms and soles of a pair 

 of duplicate twins as well as the hands of a second pair, and have shown 

 the great similarity of those parts, "which are naturally greater than 



= " Finger-Prints," 1892, p. 187. 



