INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 439 



TABLE 7 Continued 



* Two pushes. 



t Directive integration. 



J Missed latch. 



and that fluctuations in the reflex thrusts are a disturbing factor 

 in posturing. Fluctuations, then, are the production of imper- 

 fect responses. Usually these responses occur on the day on 

 which these fluctuations are noted to take place, but they may 

 appear the day after. At times these responses are not con- 

 ditioned by a fluctuation in a single ipsilateral thrust, but by a 

 fluctuation in the coordinate action of the fore and the hind 

 limbs. Sometimes imperfect responses occur when no extensor 

 thrusts can be evoked in any of the limbs, and in such cases 

 fluctuations in the neural centers of the cord for the production 

 of these thrusts undoubtedly take place, for the reappearance 

 of even a weak thrust will often produce an imperfect response. 

 It is also possible that a fluctuation in the thrusts, or a greater 

 or a more effective coordination of the limbs is favorable to 

 posturing, and imperfect responses will not appear. It is diffi- 

 cult to judge what condition of the reflex thrusts facilitiates 

 posturing under the latch. 



The facilitation of posture requires, as it must, a development 

 of an interaction of many body parts. Interaction is evidenced 

 in the widespread changes that must take place when reflex 

 excitability is manifest during learning and when this manifes- 

 tation fluctuates and wandering movements appear; it is also 



