88 K. S. LASHLEY AND S. I. FRANZ 



the door so that only three sides are exposed. The animal, 

 introduced into the restraining cage through the door (A) must 

 climb to the top of the food-box, push down the outer end of 

 the plane (B) for a distance of half an inch until the door 

 springs open, then climb down and enter the door to get food. 

 A momentary pressure is not sufficient to depress the plane and 

 the animal must maintain the full pressure while the plane is 

 moving down. The fact that he must climb upon the food-box 

 makes possible a variety of ways of approaching the plane and 

 the development of individual peculiarities of reaction. 



The methods of training were those generally employed in 

 experiments with similar apparatus. The animals, unless much 

 weakened by loss of blood, were fed only in the food-box after 

 the conclusion of the day's tests. Five trials were given daily. 



Records were made for each trial of the time required by the 

 animals to reach and push down the plane, and separate records 

 of the time taken in going from the plane to the food after the 

 plane had been tripped. Extensive notes were made of individ- 

 ual peculiarities in the path followed to the plane, of the method 

 of pushing it down, and of the path followed from the plane to 

 the food. 



III. THE RATE OF LEARNING AFTER INJURY TO THE FRONTAL POLE 



Experiment 16 As a preliminary test of the ability of the 

 animals to form complex habits after the destruction of the 

 frontal pole of the cortex a group of six animals which had been 

 used to experiments on the maze (experiments 1, 2, 3, 4, 6 and 7) 

 and had fully recovered from the operation was trained on the 

 inclined plane, described and figured above. Their behavior 

 when placed in the restaining cage was in all respects normal and 

 they learned the problem at a practically normal rate. Their 

 rate of improvement in the average time required for tripping 

 the latch is compared in figure 5 with that of an equal number 

 of normal animals trained under identical conditions. The 

 actual time consumed in learning was somewhat less than that 

 required by normal animals; their methods of learning were the 



