GENETIC TYPE AND THE ENDOCBINES 669 



and others were quick flexions of the leg or incipient flexions 

 (twitching of the flexor musculature). 



The head was also moved in a jerky fashion. At times the 

 animal raised its head suddenly and stared wildly about at 

 the slightest sound, such as a faint scratching sound made 

 by scraping the finger nail on the wall of the adjoining room. 



The head and limb movements were in every case more 

 frequent and vigorous in the interval just before the pres- 

 entation of the negative conditioned stimulus than in the 

 interval following it. During the former interval one would 

 expect the more marked evidence of nervousness since the 

 approaching negative stimulus was to be differentiated from 

 the preceding (a problem which the animal must solve). In 

 the interval following the negative stimulus, no problem is, 

 of course, anticipated, and the dog relaxes. 



The development and course of the nervous symptoms may 

 be seen in text-figure 118. To contrast clearly the increases 

 and decreases in nervousness, the total sum of the reaction 

 leg movements was registered in millimeters by the modified 

 work accumulator during the first 5 minute interval between 

 the positive and negative stimuli. The total readings during 

 each interval bore a definite relation to the total number of 

 nervous movements within the interval; the higher the read- 

 ing, the greater the number and vice versa. In the figure, 

 each bar represents the total reading for the first interval 

 in each day's experiment. It is seen at once that the read- 

 ings increased tremendously during the administration of 

 the extract and dropped back to normal shortly after the 

 substance was withheld. The increase was noticed on the 

 ninth day after treatment began (the initial increase in the 

 C-R occurred on the eighth day) and reached a maximum 

 on the twenty-eighth day (the same day when the C-R was 

 maximal). The increase was still present on the sixth day 

 after withdrawal of the substance, but then returned to the 

 normal level. This relationship between the nervous move- 

 ments and the magnitude of the C-R suggests that restless- 



