Shf.LDOK, Rrnctioiis to CliriiiKnl Sfinnili. 28 1 



]irol)al)ly })ur])osofiil only in the sense tliat; sncli a reaction is of a gen- 

 eral i)reserval ive cliarader such as is discussed by Sherrington ('()G), 

 This reaction often occurs, also, when tlie ])ectoral itself is stimulated, 

 ])artienlarly on its median margin. 



SeNSITIV' KNKSS 'i'O CuKMldAl. StIiMUI.I. 



Expcrlmcuial Besulis. — The least stimulus which will canse a re- 

 action, the comparative sensitiveness of dilferont parts of the body, 

 and the time of reaction for the different snbstances nsed are shown 

 in the tables. The data were obtained under the following conditions. 

 Several aninuils were always used for the tests and the figures given 

 are based on results obtained from two or more individuals. From 

 three to five tests were made at each point stimulated, with each solu- 

 tion used, and at each different degree of concentration of that solu- 

 tion. When individuals were used as controls, however, fewer tests 

 were made if these demonstrated that the reactions were in conformity 

 with those first obtained. Before the solutions were applied, both 

 distilled and sea water were used to make certain that no reaction 

 would result from their use, exclusive of the test solution. So much 

 variation in the reaction time between different individauls wascioted 

 that both upper and lower limit in seconds are stated for each point 

 tested. These limits differ considerably in many cases, yet it is easy 

 to see that there is a general difference in the reaction time for dif- 

 ferent regions of the body and for different degrees of concentration 

 of the solutions. For all tests on the dorsal or lateral surfaces, the 

 fish lay on the venter ; while for experiments on the ventral surface, 

 it lay on the dorsal or dorso-lateral aspect. About ten of the points 

 stimulated are omitted from the tables. 



Analysis of Results. — It will be noted that the same reactions are 

 secured by the use of any of the inorganic acids used as stimuli, that 

 is, the reactions are due to the hydrogen ions. The reactions to the 

 acids in the more concentrated solutions are very strong and definite. 

 In nearly every part of the body they take place as quickly as me- 

 chanical conditions will permit, that is to say, almost instantaneously. 

 With the decrease in concentration the reaction time becomes a trifle 

 longer. Practically the entire body is sensitive to n/20 acid, the head 



