SUMMARY 165 



flints for the construction of Lis tools, and those of the modern 

 watchmaker or scientific instrument-maker, there may have been 

 httle anatomical difference. In the application of the sense of 

 touch by a growing inteUigence, the difference would be immense. 



That the sense of touch can be highly cultivated by practice, 

 is shown in the^rapid and sldlful way in which bUnd persons 

 can distinguish the different letters of their raised type, when the 

 ordinary person of intelligence cannot find any distinction. 

 Another small development of the tactile sense in man is in the 

 imbrication of the papillary ridges referred to on the terminal 

 phalanges of the hand in certain human subjects. This arrange- 

 ment has the effect of increasing the " discriminative sensibility " 

 of the skin for the texture of various substances of which a 

 person may desire to make a judgment. If a surface, roughened 

 equally all over, such as the cover of a book, be examined, it is 

 found that the instinctive action which one makes in forming 

 tliis judgment, is to pass the tips of the fingers in a distal direction 

 or away from the body, and in a shghtly slanting direction. This 

 has the effect of bringing the imbricated ridges of this region more 

 definitely against the grain of the rough surface. If the fingers 

 be drawn with equal pressure towards the body or in a proximal 

 direction, the surface in question is felt to be markedly smoother 

 than when passed in a distal direction. This apphcation of the 

 sense of touch must have some analogous action in the lower 

 animals, for the phenomenon of imbrication is common also in 

 them. 



It were wearisome even to enumerate the multifarious 

 mechanical arts in which the sense of touch is of extreme im- 

 portance. All one need say further is, that such use of this sense 

 in man must have contributed greatly to his better equipment 

 for the struggle of his hfe and thus, in a broad way, have been 

 governed by a slow, remorseless process of selection. This first 

 use of the tactile sense is of course connected only with the hand. 



The Foot of Man. — The great importance of cutaneous im- 

 pressions in the maintenance of equihbrium has been referred 

 to, and in this use of the tactile sense, the foot of man derives its 

 main value, the prehensile function of this organ having long 



