INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 441 



TABLE 8 Continued 



* Directive integration. 

 t Missed latch. 

 J Two pushes. 



recognized in posturing when evidently many integrated, coordi- 

 nate, movements are involved, and in the disruption of these 

 movements when fluctuations in the extensor thrusts occur. 

 Interaction is again indicated, when in excessive posture a 

 greater coordinate action of the body musculature is demanded, 

 and in the necessity for reflex excitability to be manifest for 

 greater functioning of the entire body. When a greater func- 

 tioning of the entire rat's body is required, it is not a bit sur- 

 prising that fluctuations in the extensor thrusts produce imper- 

 fect responses disrupting developed interaction of body parts. 

 In the development of interaction there is evidence of a change 

 taking place in the rat, and this is seen in the decrease in the 

 extensor tone of all limbs when these limbs are functionally 

 undeveloped. When this decrease is impossible, then learning 

 is difficult or impossible. This decrease in the reflex tone 

 occurs in most rats, and particularly in the fore limbs, but it 

 may occur in the hind limbs. Of the two ipsilateral fore reflex 

 extensor thrusts, the one showing a weaker extensor tone dis- 

 appears and its contralateral remains, but in a much weaker 

 condition. This decrease in extensor tone is shown in tables 5 

 and 7, where of the two fore thrusts that were evoked in the 

 first trial, an ipsilateral fore reflex thrust alone remains. Invari- 



PSYCHOBIOLOQY, VOL. II, NO. 5 



