458 JOHN LINCK ULRICH 



plane is similar to a response to any foreign object that is placed 

 in the living cage. All movements made indicate that mani- 

 fold stimuli or the configuration of the problem are effective in 

 producing excitations in the external senses which produce 

 directive movements, and posture for progression to any part of 

 the problem box is possible. At this time, it was noted that 

 posture was essential for progression and in particular to any 

 direction to perform a difficult movement. On the other hand, 

 when the functional condition of the organism is not the best, slow 

 or rapid progression, in short or long spurts and climbing seem 

 to be the product of the functional undeveloped condition of the 

 rat's reflex mechanisms rather than from definite sensory excita- 

 tions. Numerous stimuli or the configuration of the problem 

 increase the fundamental process of progression, and it is con- 

 ducted in a variety of directions. In such cases, movements 

 become directive when reflex excitability becomes hypernor- 

 mal, but, if it is hyponormal, not until a cumulative effect of the 

 performance of a number of movements develops interaction of 

 body parts can progression occur in a definite direction. Move- 

 ments in a definite direction are not exclusively produced by 

 excitations in the external senses; but when posturing favoring 

 progression in a definite direction is possible, then the external 

 senses can produce movements to or from objects. Progression 

 is directive when it leads to touching, to smelling, or to looking 

 at any part of the problem box, such as the door or the plane. 

 An increase in reflex excitability, or the appearance of timidity 

 at this time are additional responses produced by the external 

 senses. All these movements must produce an additional 

 cumulative effect on the organism. 



Since the degree of reflex excitability manifest by rats is so 

 different, the cumulative effect produced by all responses must 

 not be the same in all rats. It was seen in the investigation of 

 learning in the latch-box problem that reflex excitability was the 

 most favorable thing possessed by a rat for solving this problem; 

 for only when reflex excitability was hypernormal, could a 

 decided cumulative effect from all movements alone reach a 

 point where responses were effectively produced. But, because 



