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KANSAS UNIVERSITY SCIENCE BULLETIN. 



reflex time. Those spots were finally selected for study that 

 proved after prolonged testing most reliable and constant in 

 their reactions to a definite stimulus. The position of the 

 chosen spots are illustrated in text, figure 1. 



It was important to find a stimulus that was of a constant 

 definite strength and that would neither injure nor fatigue 

 the peripheral nerve ending. Pure neutral filter paper three 

 millimeters square and moistened with 8 per cent pure acetic 



Figure 1. 



acid was chosen. The acid paper was placed upon the desired 

 spots with great care by means of a long, delicate forceps, so 

 as to exclude sight and pressure stimuli. That these errors 

 were avoided was proved by control experiments, during which 

 the frog's eyes were carefully covered by a specially devised 

 hood. 



By the reflex time is meant the interval between the moment 

 the paper touches the skin and the moment the frog made an 

 attempt to remove it. It was found that if the acid was not 

 rubbed off within one minute it never would be. As soon as 

 the attempt was made, or if it was not made in one minute, 

 the spot was washed oflF with fresh water. Thus fatigue and 

 injury to the nerve ending in the spot was prevented, as was 

 proved by testing the corresponding spot on the opposite side 

 of the body that had not been stimulated before. By this 



