VARIETIES IN EPIDERMIS 147 



shoulder where a weight is constantly carried, on the knuckles of 

 many manual workers, and over the patellae of a devout Roman 

 Catholic, as I have often seen. 



On the other hand what conditions more calculated to thin 

 and soften the skin could exist than those operating on the ventral 

 and flexor surfaces, axillae, groins, external genitals and the bends 

 of the elbow and knee-joints, where pressure, with little friction 

 and greater warmth and moisture prevails ? I need do no more 

 than ask which is the more reasonable of the two forthcoming 

 explanations of such phenomena, on the one hand that they are 

 adapted for, and on the other adapted by this experience ? 1 

 doubt if at any stage of the long process this slow manufacture of 

 differing fabrics ever conferred on man any survival value or better 

 matrimonial prospects. At any period or stage which I have 

 supposed it can only be claimed for the results on the skin that they 

 did not cause the animal to pass through the meshes of the sieve, 

 and theoretically might be classed among the indifferent modifica- 

 tions, even if they added a little to the comfort of their possessor. 



Skin of Palm and Sole. 



One can examine in more detail the remarkable form of skin 

 which is found to cover the palmar and plantar surfaces in many 

 mammals. It is highly specialised and appears in many degrees 

 of efficiency for the purposes, or uses, of walking and climbing, 

 grasping and discrimination of objects. With two or three in- 

 significant exceptions these are the only regions even of man's body 

 where hairs do not grow in the normal state, and in most other 

 mammals hair is absent from the component parts or pads, which 

 correspond to our palms and soles. In the absence of hairs and 

 sebaceous glands and the presence of as many as 320 sweat-glands 

 to the square centimetre, and especially the papillary ridges, the 

 mammalian hand and foot present a fruitful field for study. They 

 have been studied by none more earnestly and thoroughly than 

 Dr. H. Wilder Harris and Mrs. Wilder Harris {nte Inez Whipple). 

 This small area of skin as an organ for grasping and discrimination 

 has been studied by persons from different, but not conflicting 

 points of view. Time would fail me even to mention these, but I 

 would recall here one aspect of the matter, that is the name given 

 to it by these eminent authorities, Friction Skin. I think I do 

 them no injustice, nay even honour, when I claim them as allies 

 for us " Old Contemptibles " in the struggle, Lamarck v. Darwin in 

 respect of these characters of the " mammalian chiridium." This 

 is a term employed by them for the hand and foot of all mammals, 



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