GENETIC TYPE AND THE ENDOCFJXES 



5G7 



vigorous investigatory reactions and the refusal of food. The 

 fact that the dog retains a high level of activity is shown by 

 the continuation of the response until the experiments were 

 discontinued, and in this case the response had increased 

 slightly in intensity. This dog was employed in the experi- 

 ments over a period of 3 years, and during this time there 

 were certain intervals when the animal was not used in 

 the experiments. These intervals of rest did not affect the 

 performance. When the experiments started again, the re- 

 sponse was always as intense as it was when the last experi- 

 ment ended. 



Text-figure 1 



As in the ease of 308 6 , this dog also refused food when 

 the motor response was introduced. The animal did develop 

 definite conditioned avoiding responses, however, and could 

 differentiate between clicker rates of 84 and 120 vibrations 

 per minute. 



One dog of this group, Boston terrier 434 9, (text-fig. 100) 

 had a relatively weak conditioned salivary reaction. This 

 animal was smaller than the two discussed above, weighing- 

 less than 20 pounds, and could not be given as much food 

 during the experiments as the larger dogs. Thus it necessarily 

 follows that the conditioned reaction in this animal was much 

 smaller. It is due to this difference in size that the value of 

 the salivary reaction cannot be considered the sole criterion 

 of excitability. The total performance of 434 9 was, however, 



