INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 443 



TABLE 9 Continued 



ably when in the beginning of learning only one ipsilateral fore 

 reflex thrust can be evoked, it soon disappears, possibly to 

 reappear at intervals as is seen in table 6. In some instances 

 instead of an actual decrease in the extensor tone or the total 

 disappearance of the extensor thrust, flexion of the limb is 

 evoked. Thus a distinction must be made between extensor 

 tone and the limb remaining limp and immovable, and extension 

 of the limb passing into flexion of it. When the rat's limbs 

 remain immovable, neither set of antagonistic muscles contracts. 

 The previous marked asymmetry of the body of the rat which 

 existed in the beginning of learning, disappears as a result of a 

 reduction in the extensor tone of the limbs and a partial sym- 

 metry is established. This change with the use of many muscles 

 to attain posture is adequate for the completion of learning. 



The almost daily decreases and increases in reaction time for 

 the neck reflex movement and for directive integration can now 

 be accounted for by the occurrence of active fluctuations dis- 

 rupting developed interaction of body parts. When noticeable 

 increases in reaction time have occurred in directive integration, 

 then disruptions of this movement have carried the animal 

 some distance from the door of the problem box, and when 

 slight increases in reaction time have occurred, imperfect re- 

 sponses have appeared before the latch. When these responses 



