1?A 

 It was possible for n rat to have a perfect trial in four hpc- 

 ondP, or a failure in a less total tine. Those rate failint^ 

 to learn within one hundred days (300 trials) v/ere no longer 

 used foi- experimentation. Those rnts learnini^ the inclined 

 plcine v/ere, at the conclusion of the experiment, fed for six- 

 ty days in the runway. At the end of this period they v/ere 

 tested for I'etention and releti.rning. 



Three of the rats formed the habit of 1 if tin^^ the 

 plane at the end nearest the box and thus formin^i the contact, 

 but it apparently affected neither the rapidity of each trial 

 nor the number of days required for perfect learning. One of 

 the normal rats plaxed his nose between the electrical contacts 

 and received a shock, but beyond one squeal and a vigorous 

 rubbing, of his nose, he showed no sit;n of harm and had apparent- 

 ly forgotten the experience the next day. Some of the rats 

 jumped to the point of operation from a distance; some placed 

 the fore paws on the end of the pla.ne a,nd pressed down; and 

 still others i-an slowly around to the plane, halting an instant 

 on the point of operation, and then continued the run ciround 

 to the door. As in the maze, many of the inbred rats were sub- 

 ject to errors vvnich persisted throughout the experiment. 



The results of the experiments for the inbi'ed rats 

 fire iiiven in tables IXa, IXb , and IXc ; for the normal control 

 series in tables Xa, Xb , and Xc. These t&bles ^ive only the 

 averages of the three daily trials of individual rats. The 

 shortest period of learning for an inbred, rat was tv/elve days; 

 for a normal control, nine days. Fleven inbred rats and one 

 normal failed to learn the incl ined plane problem within one 

 hundred days. As in the maze tables, ,'ifter recordin^i the three 

 perfect days of any one rat, the average of theitime for those 

 three days was recorded on each succeeding dny in red ink. 



