On the Relation of Muscle Sense to Pressure Sense 15 



palm's front and back sides. Local stimulations in the deeply 

 lying tissues or in widely separated areas are interpreted to be 

 the results of heavier pressures. The judgment is based, for the 

 most part, upon the discovery that there is some new local sign 

 excited which had not been affected by the previous stimulus. 

 This interpretation will throw some light upon the fact that the 

 standard pressure does not always appear to be of the same 

 weight.^ The reason is that the local stimulations produced by 

 the standard pressure change from application to application. 

 Sometimes, then, a new local sign will come out with startling 

 effect and cause a judgment of heavier to be rendered. Further- 

 more, when heavier pressures approach the standard, they are very 

 likely not to excite any local signs, except those that have come 

 out some time with the standard, and hence the heavier pressure 

 is judged to be the same, since there are no local sign differences 

 that may not be due to the stimulations of the standard. The 

 stimulations that are produced by a pressure, however carefully 

 applied and removed, are many and variable, and it is a practical 

 impossibility for a reagent to take account always of the same 

 group of local signs or for the same group of local signs so to 

 fuse every time the standard is presented, that the group may be 

 always recognized or that it can be known as different from that 

 which a heavier pressure will excite. A dift'erence, sometimes 

 discriminated and sometimes not, will be due to just this fact, 

 that the local stimulations of the same pressures will now be dif- 

 ferent, and of different pressures will now be the same. 



When one compares the stimulations produced by a pressure 

 that rests upon a stationary part of the skin with those that come 

 out when the member is made to move and the skin area is 

 brought against the pressure, he will find many of the same kinds 

 of phenomena. Before- speaking of these it might be well to men- 

 tion the fact that there are likely to be accompanying visual 

 images. Sometimes the balance operates in the same way as lift- 



'The illusion of larger weights of equal heft with smaller of the same 

 external appearance being the lighter is to be explained by the fact that 

 the smaller forces the skin down upon locally different tissues within the 

 hand that have not been affected by the larger weight. 



189 



