' HABIT FORMATION IN ALBINO RATS 27 



click of the disk meeting the magnet is heard. Over the food 

 box and plane is placed a cage, C, constructed of one-half inch 

 heavy wire mesh, the base measurements of which are twenty- 

 four by twenty-four inches and the height fourteen inches. 

 This allows the rat ample room to explore all sides of and above 

 the food box. When the rat is placed within, the entrance, e, 

 to the cage is closed. 



The preliminary inclined plane experiment was not intended 

 so much as a decisive experiment as to test the efficiency of 

 the apparatus. The results, however, are significant and, there- 

 fore, included here. 



The object of this experiment was to have each rat learn to 

 reach the interior of the food box from the cage entrance in 

 the least possible period of time. The procedure of a perfectly 

 trained rat was to run from the entrance, e, to the point of 

 operation, o, remaining there until the click of the disk against 

 the magnet insured the door being open, then running through 

 the door of the box to the food which was placed within at point 

 f. The starting time was taken when the animal entered at e, 

 another when the magnet cHcked, and the final time when the 

 food box was entered. The object of recording the two periods 

 of time was that it had been anticipated that differences in, 

 association between the inbred series and the control rats might 

 appear. But, as in both series the association was practically 

 perfect by the third day, a comparison of such differences was 

 thought useless. 



In preparation for the experiment each animal, beginning at 

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

 door remaining open, ten minutes daily for five consecutive 

 days. This gave the rat an opportunity to become acquainted 

 with all parts of the interior of both box and cage, and also 

 accustomed him to a reduced feeding time. At the age of seventy 

 days the experiment began. Six males and five females from the 

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

 males and females from the normal series. All the inbred rats 

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

 regular food, bread soaked in milk. 



As one of the first rats used consumed fourteen hours before 

 his first accidental success, it was decided to use "cumulative 

 time" for the first few trials. By this method each rat was 



