100 



ficiency of the apparatus. The resultn, however, are Bi^nifi- 

 cnnt and, therefore, included here. 



The object of the experiment v/as to have each rat 

 learn to reach the interior of the food box from the entrance 

 to the cat,e in the least posnible time. The proceciure of a 

 perfectly trained rat v/as, to run from the entrance, e, to the 

 point of operation, o, reraainine, there until the click of the 

 disk against the ma^^net insured the door being open, then run- 

 ninji, through the door of the box to the food which was placed 

 v.'ithin at point f. The starting time was taken when the ani- 

 mal entered at e, another v/hen the magnet clicked, and the 

 finfil time when the food box v;as entered. The object of tak- 

 ing/ the two times was that differences in association betv/een 

 the inbred series and the control mi^^ht be compared. But as 

 in both series the association v/as practically perfect after 

 the second day such comjiarison is useless. 



In preparation, each animal, beginning at the age 

 of sixty-five days, was fed alone in the food box ten minutes 

 daily for five consecutive days. During this period the door 

 of the food uox v/as allowed to remain open, thus giving the 

 rat an opportunity to become acquainted with all parts of the 

 interior of both box and cage. At the age of seventy days the 

 experiment be^^an. Bix males and five females fi-om the inbred 

 strain were used and, as control, an equal number of males 

 and females from the normal series. All the inbred rata were 

 from the 6th generation. The stimulus used was their regular 

 food, bread soaked in milk. 



rt.s one of the first rats used took fourteen hours 

 before his first accidental success, it v:as decided to use 

 "cumulative" time for the first few trials. By this method 

 each rat was allowed to v/ork thirty minutes and then, if un- 



