GENETIC TYPE AND THE ENDOCRINES 665 



This dog was quiet, obedient and docile, somewhat shy 

 with strangers and sometimes slightly averse to the leash. 

 Defending himself well from attacks by other dogs, he rarely 

 took the offensive except when his food was approached by 

 another dog. 



Since experiments of this sort deal with the accomplish- 

 ments and performances of the individual, what the animal 

 can do, in terms of conditioned reflex action, it is important 

 to present the detailed results of behavior with such concepts 

 in mind. Thus we shall present for every animal the efficiency 

 of his response, i.e., how often he responds in a correct and 

 biologically appropriate manner in a given number of trials, 

 together with the magnitude of the response. In this way 

 one can best study the nervous system operating under normal 

 conditions and under altered physiological states. We shall 

 give the percentage of correct conditioned responses to both 

 positive and negative stimuli and the average magnitude of 

 the reactions to the positive stimulus. 



The C-R in dog 814 $ was formed after fifteen trials and 

 was fairly stable. 



The animal was fed thyroid extract 9 1 gm. daily for 23 

 days. Behavior was essentially unchanged during the thyroid 

 feeding, the C-R remaining approximately as before. 



Table 8 shows that the percentage of correct responses to 

 Met. 120 remained exactly the same during the extract treat- 

 ment but declined (82 per cent to 70 per cent) after the 

 extract was withdrawn. The negative response increased in 

 efficiency (60 per cent to 71 per cent) and afterward decreased 

 slightly (66 per cent). The magnitude of the C-R was prac- 

 tically unchanged during the experiment. The dog's general 

 behavior underwent no detectable change during or after the 

 thyroid period. 



All gland extracts used in the present investigation (with two exceptions) 

 were furnished by the research department of Eli Lilly and Company. The ex- 

 ceptions were an extract of the suprarenal cortex (eschatin Parke-Davis) and 

 a general extract of the anterior lobe of the pituitary (growth extract Squibb). 



