PHYSIOLOGICAL PARADOXES. 



But the nerves are very different from the 

 wires in one respect, the speed at which they 

 carry their messages. The electric current 

 passes along wires at a speed which would 

 enable it to make the circuit of the world a 

 good many times in a second ; for small dis- 

 tances it is practically instantaneous. The 

 speed of the message along the nerves is not 

 nearly so great. It has been found on measure- 

 ment to be between thirty-five and fifty yards 

 per second. 



There is, therefore, an appreciable time 

 during which an order is being transmitted 

 from the ear or eye to the brain, and another 

 interval while the stimulus from the brain is 

 passing along other nerves to the muscles which 

 have to act. 



Theoretically, then, it is impossible for the 

 most willing servant to obey immediately, 

 though practically it makes a great deal of 

 difference whether the bell or signal be the 

 one to begin work or to cease work. 



4. False Continuity in Sense of Touch. 



The sense of touch is limited, like the other 

 senses, as to the possible fineness of our ob- 

 servations. 



The skin of the back and of parts of the arms 

 cannot distinguish between points which are 

 two inches or more apart. If the point of a 



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