

TOUCH. 149 



What is pressure sensation? 



When weight is added to an ordinary touch, the sensation of the 

 pressure of the weight is felt, and by it one can judge with con- 

 siderable accuracy the amount of the pressure, and determine the 

 comparative pressure of two weights with approximate correct- 

 ness within limits of pressure. This is known as the sense of 

 pressure. 



What is the muscular sense? 



By taking a body in the hand and raising it we feel a sense of 

 resistance in the muscles, by whose intensity we can much more 

 accurately determine the weight. This is the muscular sense. It 

 is developed to an exceedingly fine degree in some occupations ; 

 for example, postal clerks detect overweight letters with wonderful 

 accuracy and quickness. 



What is the origin of the muscular sense ? 



It has been urged that the muscular sense is of central origin, 

 and depends upon the strength of the impetus which must be 

 sent to the muscles to cause them to do certain work. It may, 

 however, be due to a training of the sensibility of the muscle, 

 whereby the relative strength of a contraction is perceived as a 

 sensation. 



What is temperature sense? 



The surface of the body is very sensible of temperature changes ; 

 and that this is distinct from ordinary tactile sensation has been 

 inferred from the fact that when the ordinary touch is blunted the 

 temperature sense may remain unimpaired. 



Are the sensations of temperature accurate from a thermometric 



standpoint ? 



No. They are relative ; that is, we infer from the temperature 

 of the skin or of our habitual surroundings the warmth or coldness 

 of the thing tested. It is related that Arctic explorers have found 

 the water feel warm when swimming in pools on icebergs, and a 

 drop of the mercury to 80 F. is said to feel cold in torrid climates. 

 A more simple illustration is that of immersing one hand in water 

 at 40 F. and the other in water at 120 F.. and then both in water 

 at 80 F.. when one hand will feel hot and the other cold, though 

 both are subjected to the same temperature. Again, during a chill 

 the temperature of the body is often very considerably elevated, 

 and yet the sensation is entirely of cold. 



