198 ALBERT If. REESE 



All nine of the animals responded to a .25% solution, but more 

 slowly and less violently than in the preceding cases. All nine 

 animals responded fairly quickly and violently to a .125% solu- 

 tion when the head was stimulated ; all but one responded when 

 the tail was stimulated, and two of these bit at the spot affected. 



All nine animals responded fairly strongly to head stimulation 

 with a .0625% solution, though some responses were very slow. 

 Three or four gave no response to tail stimulation, though one 

 which did respond bit at the spot stimulated. 



All of the animals responded to a .03125% solution on the 

 head, though the response was very slow and usually not strong. 

 Only one animal responded to stimulation of the tail, but that 

 one bit at the spot stimulated as though the irritation were 

 considerable. 



All but two of the animals responded to a .015625% solution 

 when the head was stimulated ; the reaction was, of course, very 

 slow. No reaction was obtained from any of the animals when 

 the fluid was squirted against the tail. 



A .0078125% solution produced a response in only one animal 

 when the head was stimulated, and no response was obtained 

 from any of the animals when other parts were stimulated. 



Experiment 7. For reactions to acids various strengths of 

 hydrochloric and glacial acetic were tried. Since no difference 

 in the reactions was noted, except that, as might be expected 

 the hydrochloric acid acted more strongly for a given concen- 

 tration, the experiments with only the acetic acid will be 

 described . 



As was said above, experiments were tried to determine 

 whether one part of the animal was more sensitive to chemical 

 stimulation than another, but with the exception of the head, 

 all parts of the body seemed to be about equally sensitive. 

 Whether it were the nostrils, mouth, or eyes that caused the 

 greater sensitiveness of the head it was difficult to determine, 

 since, on account of the small size of the animals, it was almost 

 impossible to stimulate one of these structures without the other. 

 By carefully controlling the direction of the jet from the pipette 

 it was possible to oause most, if not all, of the fluid to escape the 

 eyes, and no difference was noticed in the reactions of the animals 

 so stimulated from those in which the jet was directed upon the 

 top of the head as a whole. The relative sensitiveness of the 



