of food, necessary. It was early seen how a healthy 

 metabolism was needful to success in learning. 

 LATCH BOX. 



The latch box was the first problem worked with. 

 All that was necessary to solve the problem was to open 

 the door of the box. The solution was accomplished by 

 the rats, either by raising the latch with their snouts 

 or by some more complicated method. The snout was 

 usually the agent for entrance, though not always the 

 first adopted. 



In the beginning of the work on this problem it .vas 

 thought necessary, when taking rats at forty days old, to 

 give a few preliminary daily runs in a square maze of 

 the Hampton Court type, before actual experimentation. 

 This was only done to familiarize young rats to strange 

 surroundings and to accustom them to being handled. 

 This eparation was continued in all the work with 

 latch box when used alone, but was given up as unnec- 



