256 ARCHIVES OF NEUROLOGY AND PSYCHIATRY 



the floor of which a small problem-box containing food was bolted. 

 Three problem-boxes were used : 



1. Pull box. The animal must reach through a circular hole. 2 

 inches in diameter, grasp and pull forward a rod which passed trans- 

 versely 3 inches behind the hole. This released the lid of the box, 

 which was thrown open by a spring. 



2. Crank box. The animal must grasp and turn a crank projecting 

 from the front of the box. The crank handle described a 6 inch circle. 

 It offered a resistance of about 200 gm. at all points of the circle. It 

 was set at "one o'clock'' and must be turned counter-clockwise through 

 270 degrees, at which point it released the lid of the box. The lid was 

 thrown back by a spring. 



3. Hasp box. The animal must open an ordinary gate hasp, closed 

 with a wooden plug inserted loosely through the staple, withdrawing 

 the plug and lifting the hasp from the staple, over which it would fall 

 again if released. He must then raise the lid of the box and hold it 

 open while he reached in for the food. 



Five trials a day were given with each box ; the time spent in each 

 trial was recorded, and detailed notes were made as to the use of right 

 or left hand and the exact method employed in opening the boxes. 

 Training was continued until the latches were released in a stereotyped 

 manner without random movements. Several interruptions of training 

 occurred lasting from one to several weeks, so that the learning curves 

 do not represent the rate for continuous training. 



In addition to the problem-box habits, each animal was trained to 

 pick out cubes of banana from among cubes of wood of similar size 

 and appearance. The cubes were scattered in irregular order under a 

 sheet of glass supported 2 inches above the floor of the cage. They 

 were placed about 6 inches back from the edge so that the animals had 

 to reach under the glass to get the cubes, which they could see but 

 could not distinguish by odor. 



Operative Technic. — Destruction of the motor areas was made under 

 ether anesthesia, with aseptic precautions. The region of the precentral 

 gyrus was exposed by trephining and identified by electrical stimulation. 

 The opening was enlarged by bone-forceps until the precentral gyrus 

 and surrounding areas were exposed. Arm, leg and face areas were 

 verified by stimulation, and the limits of the excitable area determined. 

 The entire area was then undercut by thermocautery to a depth of 

 about <> mm. To avoid injury to the longitudinal sinus, a median bridge 

 oi bone, 1 cm. in width, was left intact. In one specimen the leg area of 

 this region was undercut by passing the cautery diagonally mediad and 

 downward until the resistance of the falx was felt, then cutting longi- 

 tudinally across the gyrus. The dural flaps were then replaced and 

 the wound closed. In the cases reported below the wounds healed with- 

 out infection. 



