INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 399 



the latch may be pushed only part way out of the notch and the 

 neck reflex movement not completed. The body then is inade- 

 quately postured. Sometimes in excessive posture, the teeth of 

 the rat are fixed in the wire mesh of the door under the latch and 

 the body swayed back and forth and gradually raised. This 

 upward movement eventually pushes the latch out of the notch, 

 or at the moment excitations are produced from the moving 

 latch, the hold on the wire mesh is released, and the neck reflex 

 movement is produced. In such instances as the last, the stimu- 

 lus of the moving latch becomes prepotent over touching the 

 latch, and the neck reflex movement follows. Again, the teeth 

 may be fixed in the latch and the latch raised out of the notch. 



The appearance of posture to produce the neck reflex move- 

 ment is dependent upon a degree of manifestation of reflex ex- 

 citability. The most satisfactory performance of the neck reflex 

 movement to raise the latch on the first trial and during learning 

 follows a reflex adjustment of the body or posturing, and in some 

 way the presence of reflex excitability is essential. Usually dur- 

 ing and after posturing, an evident increase in excitability is 

 manifest. Slight displacement of the latch not only increases 

 posturing, but also increases reflex excitability which seems to 

 aid the continuation of the performance of the neck reflex move- 

 ment. Reflex excitability is again greatly increased in some rats 

 after the neck reflex movement is produced. Rapid progression 

 may occur in a direction away from the door, even around the 

 problem. Feeding then does not commence immediately, but 

 progression is continued in and out of the problem. Hunger 

 excitations are evidently absent during manifestations of reflex 

 excitability, and this in accord with the findings of Cannon (8) 

 and Carlson (9) who have shown that in states of emotional ex- 

 citement, peristaltic movements of the alimentary canal for the 

 production of hunger excitations are inhibited. Only when reflex 

 excitability subsides does feeding begin. 



Hunger must also be absent or its excitations must be inef- 

 fective when inaction is present. Excitations as a result of con- 

 tractions of the alimentary canal, can not for some reason be 

 effective unless the mechanism of reflex excitability, and probably, 



