CEREBRAL FUNCTION IN THE RAT 



87 



finally selected as combining a fairly specific reaction to a definite 

 series of stimulating objects with relatively complex kinesthet- 

 ic-motor habits. In order to complicate the kinesthetic habits 

 somewhat and allow of greater individual variation than is 

 possible in the usual type of this problem-box, the design shown 

 in figure 4 was adopted. The problem-box consists of a wire 

 covered rectangular frame- work having a door (D), held open 

 by a pair of flat brass springs, compressed between the door 



FIG. 4. THE INCLINED PLANE Box 



A, door of restraining cage; B, inclined plane; C, catch extending down to 

 upper edge of door, D, door leading into food-box. 



and its frame. On top of the box, above the door is a board 

 (B), supported in the middle by a metal fulcrum and weighted 

 so that the end C is slightly heavier than the other. From the 

 board an adjustable metal rod (C) extends through the top of 

 the box to the door and serves as a latch to hold it closed. A 

 pressure of from 50 to 75 grams at the free end of the plane 

 (B) is required to tilt it and release the door. This, the food- 

 box, is enclosed in a larger restraining cage having a door at 

 A and is pushed against the side of the restraining cage opposite 



