148 INITIATIVE IN EVOLUTION 



and is very convenient for descriptive purposes. From this point 

 of view this organ has been produced from more generalised ancestral 

 structures by reason of friction and pressure, and not for the 

 purpose of resisting them, at least in their initial stages — again, 

 adapted by and not adapted for meeting those forces. There are 

 other views of the matter held by Pan-Selectionists, notably that 

 of Dr. Hepburn, in regard to the papillary ridges. He would, as I 

 gather, treat them as primarily induced, by selection, for the better 

 grasping of objects cylindrical or more or less globular. I have 

 referred elsewhere 1 at some length to this in a book describing the 

 examination of the hands and feet of eighty -six species of mammals. 

 The varieties of epidermis were divided into the smooth, corrugated, 

 scaly, nodular, hairy, rod-like and ridge-covered forms, also four 

 mixed varieties, such as corrugated with coarse transverse ridges on 

 the digits, corrugated with papillary ridges, nodular with papillary 

 ridges, and hairy with coarse transverse ridges and smooth pads. 

 Of these the species with smooth ejridermis and hair are few and 

 unimportant, and the largest group examined was that of the 

 Primates, thirty in all, in which papillary ridges were always present. 

 It is highly probable that the causes of these modifications of the 

 epidermis in diverse groups of animals could be traced to the habits 

 and modes of life of each, but I make no attempt here to do this. 

 It is also matter for inquiry, upon which no agreement has apparently 

 been reached, how it came to pass that man has virtually lost his 

 hairy coat, and in regard to the palms and soles of animals, what 

 may be the reason that so few have any hair on them, and why 

 man has no sebaceous glands, but has very numerous sweat-glands 

 in these regions. 



This is all of great interest, and possibly some day the 

 Mendelians will solve for us the mysteries thereof. But here I 

 need only ask how it would have been possible for hairs to grow, 

 or, if growing, not to be promptly worn away on a surface used by 

 animals from monotreme to man for walking-pads, and by most 

 of them also for grasping and discrimination between objects as 

 well. We are so familiar with the thickening of the skin on the 

 hands of manual workers and on the feet of those who walk much, 

 to say nothing of what we call a " corn," from pressure of tight 

 boots, that we are in danger of forgetting that the protecting skin 

 over the hands and feet of animals was of necessity adjusted in a 

 crude way to the measure and kind of walking in past ages and in 

 all levels of life, and that it is maintained in that adjusted condition 

 by the use, or disuse, of each life. Another familiar example is 



1 The Sense of Touch in Mammals and Birds. A. & C. Black, 1907. 



