ARRANGEMENT OF THE PAPILLARY RIDGES 159 



a good light and flexing the fingers slightly, which brings nearly 

 all the ridges adjacent to the joints into directions parallel with 

 one another, the greater lengths of D 3 and 4, and their closer 

 functional connection with one another, producing thus a transverse 

 arrangement, and in D 1, 2 and 5 a more oblique one. In the palm 

 this correspondence of ridges with flexion lines of joints is not found 

 so much except in the central part of this surface. But the oblique 

 and longitudinal ridges of the palm where it becomes concave in 

 the action of folding the hand over a globular object are well shown 

 there also to correspond with such action. 



This general grouping of ridges is seen, mutatis mutandis, to 

 belong to all the palms and soles of lower Primates, and the illustra- 

 tions given will speak for themselves, so that little need be said 

 on each. 



Reasons for Arrangement Observed. 



When one discusses the forces in action on man's hand which 

 are claimed to have thus arranged the ridges, in regard to the 

 question of use and habit, little more need be added as to those 

 of other Primates, and it is because we know more about ourselves 

 than them, and our own palms and soles are available for inspection, 

 that I have taken man as the example. 



The main question is the old and now familiar one : " Are 

 these ridges arranged as we see them by use and habit, or adapted 

 for use ? " Dr. Hepburn and the orthodox Selectionist would say 

 that, of course, their mode of arrangement is an adaptation governed 

 by selection for preventing slipping in the action of grasping an 

 obj ect by the hand, and in the foot for preventing slipping in walking. 

 This does not take into account the question as to how the original 

 slight shifting of the ridges in the earliest man and in lower forms 

 could have had selective or survival value, for example, the in- 

 significant sparse groups of ridges on the palm, sole and tips of 

 the digits in a hedgehog or squirrel. As things are now they do 

 subserve these purposes. But I think this matter of prevention 

 of slipping has been much exaggerated, though I may be told that 

 this is a matter of opinion and not a valid argument against the 

 hypothesis. 



Foot of Man. 



The point may be best understood by considering the foot of 

 man, of which Fig. 60 shows a good example. The value of the 

 roughened surface of the foot with its papillary ridges can hardly 

 have been great, even in the days when man's foot was naked, 

 at any rate so little that for him to acquire by a selectional process 



