128 Journal of Comparative Neurology and Psyeliology. 



2. Electric Stimulation and Sound. 



Inasmuch as the experiments here described were con- 

 ducted in a laboratory where noise and jar are unavoidable, it is 

 worth while at this place to offer reasons for the belief that 

 sounds did not to any considerable extent affect the time of re- 

 action to other stimuli. 



As tests of the influence of loud sounds on the electric re- 

 action-time, an apparatus was arranged whereby an electric bell 

 rang for a certain interval before the electric stimulation. The 

 bell was placed 40 cm. from the frog, and for one series of 300 

 reactions it rang o. i second before the electric stimulation, for 

 another i.o second before. The reactions were taken in pairs, 

 first a reaction to the electric stimulus alone, then one to the 

 electric stimulus preceded by the auditory, at the rate of one a 

 minute. The results may be summarized, without mention of 

 other values than the means, thus : 



j Average of 300 reactions to 2 Cell Electric Stimulus Alone, 172.0 6 

 Series I. -I Average of 300 reactions to 2 Cell Electric Stimulus, when preceded 

 I for 0.1 second by Auditory Stimulus, 176.5 6 



j Average of 300 reactions to 2 Cell Electric Stimulus Alone, 144.7 ^' 

 Series II. -/ Average of 300 reactions to 2 Cell Electric Stimulus, when preceded 

 I for 1.0 second by Auditory Stimulus, 150.2 6 



In each of these series there is evidence that the sound 

 caused slight inhibition or delay of reaction, but when we con- 

 sider, as will be made clear later, that the probable error of the 

 averages is greater than the apparent delay, it is at once evi- 

 dent that we can not safely argue from these results to the in- 

 hibitory influence of sound. Indeed most observations on rec- 

 ord tend to show that audition is not very important in the frog, 

 at least when it is out of water. 



3. Electric Stimulation and Moving Object. Preliminary Experi- 

 ments. 



For the purpose of determining the effect upon reaction- 

 time to an electric stimulus of stimulation of the eye by a 



^ The conditions were not precisely the same for the two series, as the frogs 

 had become inactive. 



