TEMPERATURE SENSES IN FROG's SKIN 89 



The surface of the foot was the only area treated. Sometimes 

 one foot was stimulated and the other kept as a check, but in 

 most cases there was an alternate stimulation of the normal feet, 

 or of the norir^al and the treated foot. Baths of water and ap- 

 plications of stimuli were given at definite intervals which were 

 kept uniform through each experiment. Preliminary experi- 

 ments were made with each different kind of stimulation in 

 order to find out what reaction might be expected. 



At each test a definite allowance of time was given, and if the 

 reaction did not occur within that period the stimulus was 

 regarded as producing no reaction and recorded as o°. In the 

 tables the period just described is termed the reaction allowance. 

 The interval which actually elapsed between the application 

 of the stimulus and the reaction was taken in seconds with a stop- 

 watch and recorded with the description of the response. No 

 periods less than half a second were recorded. Intervals wliich 

 separated stimulations sufficiently to prevent exhaustion were 

 also selected by experiment. These have been designated the 

 stimulation intervals. 



During the experiments the normal feet were kept in 'bath 

 water' unless actually undergoing stimulation. In experiments 

 made under cocaine treatment the foot was always returned to 

 the cocaine solution after it had been immersed in the stimulant. 

 In the preliminary part of this work a good deal of trouble was 

 experienced by the washing out of the cocaine, so this procedure 

 was found necessary. A solution of 1 per cent cocaine was the 

 only anaesthetic used. 



OBSERVATIONS 



Responses to heat 



The first experiments of this series were made in order to deter- 

 mine whether the frog's foot would regularly react to heat, and 

 if so to what degree of heat. A typical heat response was also 

 looked for, a position or movement which should recur in many 

 different individuals. Both feet of the experimental frog were 

 kept in normal condition. In the first experiments considered 



