On the Relation of Muscle Sense to Pressure Sense 



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the same way, he will not feel the weight in the same way or in 

 the same place. The strains brought out by the weight will shift 

 from place to place, and in successive liftings they will appear 

 in differently localizable parts of the lifting member. Fechner 

 called attention to what he has termed the natural mode of mak- 

 ing discriminations, which is through a combination of what has 

 been called since Weber's time pressure and muscle senses. This 

 distinction has been uncritically accepted and retained. Our 

 problem has been to show that they differ only m the greater 

 freedom of movement in the so-called muscle sense. Pressures 

 and movements are found in both only in different proportions. 

 •Introspective study, oft and carefully repeated, has failed to 

 reveal anything that can with much propriety be called pressure 

 sense. If one allows a pressure to rest upon the hand for more 

 than a few moments, unless the amount be equal to a pound's 

 weight or more, the pressure will scarcely produce any effect at 

 all. Unless some slight muscular twitchings arise now and then 

 to increase or decrease the pressure for a moment, the effect will 

 soon disappear and remain unobservable. If, however, one stud- 

 ies the effect of the pressure exerted by the cork used in these 

 experiments from the moment it is applied, he will discover that 

 the pressure is felt now in the skin beneath the cork, now in the 

 increased area of contact of the hand's back with the support 

 through the recession of the hand from the pressing cork. 

 Again, on the skin there will be no pressure at all, but a stretch- 

 ing of the skin, first in one radius and then in another, running 

 ou't from the cork as a center. Furthermore, although every care 

 has been taken to make the cork set upon the skin with perfect 

 evenness, the contact is felt now in one part of the cork's circum- 

 ference and now in another. In addition to all these differences 

 one will feel, first here and then there, a twitching of the muscles 

 in the palm. One muscle vibrates, another contracts, another is 

 strained, and another is relaxing. First one of these factors and 

 then another is the object of attentive action. The twitching or 

 increased tension of one muscle from one application to another 

 may shift the tension or the place of pressure in the skin, and so 

 change the locations of the stimulations. If, now, one will care- 



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