CONTENTS 



Page 



Acknowledgments v 



Introduction 1 



Historical 1 



Apparatus and Procedure 4 



Experimental Results: 



Twenty-five day rats 15 



Sixty-five day rats 23 



Two hundred day rats 29 



Three hundred day i ats 33 



Five hundred day rats 38 



Comparison of Results for Different Ages 42 



Incidental Tests: 



Effect of Sex on Rapidity of Learning 46 



Day and Night Work 47 



Continuation of Work after Problem has been Learned 48 



Blood Relationship and Learning 51 



Retention 52 



Resume of Conclusions 54 



