GEXETIC TYPE AXD THE EXDOCRIXES 



667 



TABLE 9 

 Dog 868 £ 



Correct responses to positive Met. 120 

 Correct responses to negative Met. 28 

 Average magnitude of C-R to 

 positive Met. 120 



TRAINING DURING 



PERIOD EXTRACT 



1 MONTH 



AFTER EXTRACT 



WITHDRAWN 



the administration of the extract (94 per cent to 91 per cent). 

 The percentage showed a sharp drop, however, after the 

 substance was stopped (91 per cent to 75 per cent). The 

 percentage of correct negative responses increased somewhat 

 (61 per cent to 73 per cent) and increased further in the 

 after period (100 per cent). 



The average magnitude of the C-R to Met. 120 increased 

 considerably during the administration of the substance 

 (twelve to eighteen) and fell after it was discontinued (to 

 nine). 



These percentages and averages obviously show only cer- 

 tain trends. The magnitude of the effect of the thyroid 

 substance upon the responses is masked to a considerable 

 extent by the statistical treatment. It is readily seen that 

 since the effect of the extract is not revealed immediately 

 after the first treatment but is apparent only after a lapse 

 of a week or 10 days, and since the effect outlasts the ad- 

 ministration period by as long as 2 weeks or more, the 

 statistical records confined exactly to the administration 

 period, or to a succeeding period when no extract was 

 given, cannot present the exact history of the effect within 

 the periods themselves. For these reasons it is of advantage 

 to illustrate graphically the entire course of the C-R during 

 the experiment. We shall accordingly present charts as well 

 as the tables for each experiment in which the facts can thus 

 be better presented. 



Text-figure 117 is such a chart. The reflex showed a notice- 

 able increase on the sixth day after the extract was begun, 

 and this reached a maximum on the twenty-eighth day. The 



