GENETIC TYPE AND THE ENDOCRINES 657 



Discrimination was established when the dog reacted to the 

 fast rate and gave no reaction to the slow. Both signals were 

 presented during the same day's experiments. 



The procedure in representative experiments was, in gen- 

 eral, as follows: The day's testing of the salivary conditioned 

 reflexes was begun by presenting the metronome 120 for 3 

 seconds followed at once by food. This short conditioned 

 stimulus served to keep the animal alert for food as associated 

 with the metronome. After an interval of 4 minutes, the 

 following stimulations were always applied: metronome 120 

 sounded for 20 seconds, then food; pause of 4 minutes; 

 metronome 28 sounded for 20 seconds, no food; pause 4 

 minutes; metronome 120 sounded for 20 seconds, then food; 

 animal released. The testing of the motor conditioned re- 

 flexes was done similarly. In these tests the initial short 

 stimulation was found unnecessary since the dogs were 

 normally always alert in anticipating the shock. The follow- 

 ing stimuli were applied: metronome 120 sounded for 10 

 seconds, then shock; pause of 5 minutes; metronome 28 

 sounded for 10 seconds, no shock; pause of 5 minutes; metro- 

 nome 120 sounded for 10 seconds, then shock; animal released. 



The metronome 120 followed by food or by shock, and the 

 metronome 28 or 42 never followed by food or by shock, will 

 henceforth be referred to as the positive and the negative 

 conditioned stimulus, respectively. 



Occasionally the order of presenting the various stimuli 

 was altered to prevent the animals from forming a " position 

 habit" (response to the order of the stimuli per se). At times 

 the series began with the negative, metronome 28, no shock, 

 and at other times the series ended with this stimulus. Such 

 procedure disrupted any tendency to react in a certain way 

 to a certain place in the series. Thus the clogs appeared to 

 listen closely to the rate of the beating metronome. 



A total of twenty-one trained dogs was used. The condi- 

 tioned salivary reflex was formed in thirteen and the motor 

 in eight. In the training experiments, seven normal dogs 

 were employed for studying the effects on behavior of the 



