478 JOHN LINCK ULRICH 



trial; in table 15 to the door in the fifteenth trial, to the plane 

 in the nineteenth trial, and directive integration was not com- 

 pletely facilitated until the twenty-first trial. For some defi- 

 nite reason, different parts of directive integration are not facili- 

 tated at the same time, and its complete appearance is greatly 

 delayed. 



Directive integration is not established or facilitated until 

 speed is gained, and this soon occurs when reflex excitability is 

 hypernormal. Before speed is gained, movements are undi- 

 rected, and no definite movements are constantly performed. 

 The records of rats presented in the last three tables reveal the 

 inconstancy of all responses, until reflex excitability becomes 

 hypernormal, and the extensor tone of all integrated reflexes 

 for posture to produce movements is facilitated. Wandering 

 movements, progression either to the right or to the left of the 

 problem to the plane and repeated advances to the plane, occur 

 until movements are directive. Fluctuations in the reflex 

 thrusts frequently become less, which means that progression 

 direct to the plane or to the door is easily facilitated. That 

 which requires a long time to accomplish in rats that manifest 

 hyponormal reflex excitability and have undeveloped reflex 

 thrusts, is present almost at the outset in rats with functionally 

 developed reflex mechanisms. 



When movements are more regularly directive then one 

 method is generally used to plunge the plane. Either the plane 

 is stepped on during rapid progression around the problem, or 

 the modified thrust is used to bring the plane down. Not one 

 of these methods is as efficient as the extensor thrust, for out of 

 60 trials very few consecutive perfect records are obtained, and 

 at times only isolated perfect records are made. Table 13 

 shows only 3 perfect records and table 15, only 2. The employ- 

 ment of one constant method does not increase the number of 

 perfect records, and this fact indicates that excitations in the 

 external senses have definite limitations. Only after training 

 can such excitations produce some effective responses. 



The indefiniteness or the slowness with which some responses 

 appear to be produced when reflex excitability is hyponormal in 



