13 

 an interval of sixty days. In the very beginning of this 



work, the rats were tested after thirty days, but retention 

 seemed so perfect at the end of this time that the inter- 

 val was increased to sixty days. In the meantime the 

 rats were not left idle but were still fed onoe a day 

 after being again allowed to run in the square maze to 

 keep them in trim. They were even permitted to run about 

 after feeding. Thus the evils arising from close confine- 

 ment to cage life were in a measure avoided. Several days 

 before the retention tests were made, the freedom of the 

 maze was restricted and the rats put back in the cage as 

 soon as hunger was satisfied. This was done in order to 

 prevent overfeeding and to again accustom them to short 

 diets. Just before a retention test was taken, the rats 

 were run once through the square maze. The tests were 

 taken for two days only and no attempt at relearning was 

 made. All that was desired was to determine how per- 

 sistent was the habit formed. 



