22 

 were given. will be discussed later. 



The results obtained from these experiments show 

 that one trial daily is the most economical in the way 

 of trials. This demonstrated fact suggested further work 

 on the latch box and trials were given some rats every 

 other day and other rats every two days, that is .with two 

 days intervening between successive trials. 



This particular problem was conducted under the same 

 conditions and with the same strain of rats as the pre- 

 ceding work. The days on which the rats were not required 

 to solve the problem, they were allowed to run in the 

 square maze to keep down body weight. This was not suc- 

 cessful in every case, as some gained weight very rapidly 

 but their activity was not noticeably effected. A more 

 satisfactory group of rats could not have been secured 

 than the ones used in the experiment. They were of an 

 unusually hardy strain. 



The data from this experiment was still more surpris- 



