GENETIC TYPE AND THE ENDOCRINES 



589 



with which the reaction appears in the animals or the fre- 

 quency with which they receive the shock after the response 

 once occurs, serves as an indication of the degree of nervous 

 excitability. The lethargic group received the shock more 

 frequently than the active, tense group. In some active ani- 

 mals the signal appeared to be intense enough to elicit two 

 or more avoiding movements before the association between 

 the signal and the movement disappeared and the animal 

 was shocked again. These ratios may be shown by indicating 

 the number of true avoidance reactions to 100 signals. More 

 than 400 signals were given to all the dogs, and in most cases 

 more than 500. It was not necessary, however, to give this 



Text-figure 104 



number in order to arrive at an indication of the general 

 degree of excitability of the dogs. If the animal is excitable, 

 it is apparent as soon as the reaction is formed. The sluggish 

 nature is also apparent from the beginning of the experiments, 

 since these dogs are not greatly disturbed by the shock. 

 The number of responses given to 100 signals is shown in 

 text-figure 104. 



The animals of group A, having a low response value, 

 are on the left side of the chart. For example, 1427 9 , 863 $ , 

 and 709 9 did not form a true conditioned avoiding reaction. 

 Animal 251 $ gave a continued avoiding response in only 

 two of the 100 applications of the signal. For the other 



