DOES IT TAKE TIME TO THINK? 569 



muscular contraction require time. Had these been considered, the 

 solution would have been farther from the truth than it really was. 

 Recent investigations of more precision have not, however, given re- 

 sults that differ widely from that obtained by Haller. The rate as 

 given by Helmholtz, after many experiments, is about 111 feet per 

 second. This is now generally accepted as the most accurate state- 

 ment. Slight differences in results for movements from the brain, and 

 for those proceeding to it, have been obtained in the investigations, 

 but the rate is regarded by the best authorities as essentially the 

 same for both movements. If there be a difference, it arises because 

 the rate of voluntary impulses moving from the brain outward is the 

 more rapid of the two. 



A difference also has been found to exist in the rapidity with 

 which we perceive impressions received through the eye, and those 

 received through the ear. This at one time was supposed to be 

 caused by a difference in the rate of transmission in the respective 

 nerves. The better authority now is that the disparity is occasioned 

 either by difference of length of the two nerves, or because the mind 

 does not so readily distinguish impressions of one kind as those of 

 the other. 



If these data are correct, it requires at least one-twelfth of a sec- 

 ond for us to perceive a sensation in our foot. A mosquito which 

 selects our ankle as the field of his operations has nearly a sixth of a 

 second in which to make his escape, for it requires at least one twelfth 

 of a second for us to find out that the mosquito is there, and another 

 twelfth of a second for us to make up our mind to declare war upon 

 him and to initiate hostile action. 



It will be observed that the rate of nervous transmission is com- 

 paratively slow. Electricity travels at the fate of many thousand 

 miles a second, or, more accurately, 16,000,000 times as fast as nervous 

 action. Light moves about two-thirds as fast as electricity. If we 

 examine movements which are comparatively sluggish, we find that a 

 cannon-ball, when fired, moves about 900 feet a second, or nearly ten 

 times as fast as nervous energy. A railroad-train speeding along at 

 sixty miles an hour would be moving at about the same rate as an 

 ordinary nervous stimulus, though in a contest the stimulus would 

 probably win. 



By further experiment it has been determined that the time re- 

 quired for the excitation of the muscular fibres for such acts as the 

 supposed pressing of the button, this being the factor last in order of 

 the entire six, is about one-hundredth of a second. 



It is also declared with some precision, both by analogy to this 

 last act and by experiment, that the time required for the reception of 

 the impression by the sensitive membrane, which is the first and a 

 corresponding factor of the complete physiological time, is also about 

 one-hundredth of a second. 



