GENETIC TYPE AND THE ENDOCRINES 



675 



A still further slight diminution in the percentage occurred 

 during the second thyroid treatment (9 per cent). The per- 

 centage of correct responses to the negative Met. 28 increased 

 from 92 per cent to 100 per cent during the first experiment 

 and from 93 per cent to 100 per cent during the second. The 

 average was quite unchanged. 



Viewed as a whole, the values represent a gradual de- 

 terioration of the positive conditioned response (68 per cent 

 30 per cent 17 per cent 12 per cent 9 per cent) associated 

 in some way with the advancing stages of the l ' experimental 

 neurosis." 



Summary of the thyroid effects. It is clearly apparent that 

 in dog 814 there was little or no effect on the C-R that could 

 be attributed directly to the thyroid extract. Since the slight 

 increase in correctness of the negative continued after with- 

 drawal of the extract,, it was probably due to training rather 

 than to the extract. 



In dog 868 (motor C-R), the extract had a decided effect 

 on behavior. The dog became generally more excitable, and 

 this excitability diminished when the extract was no longer 

 given. The total behavior picture indicates clearly a rise in 

 the general level of nervous excitability. The C-R was aug- 

 mented and the animal was more restless between experi- 

 ments. As in dog 814, the increase in efficiency of the negative 



