INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 405 



The only means to determine the undeveloped reflex mechan- 

 ism was to test the living rat for the neck reflex movement and 

 its interaction with other reflex mechanisms. Three different 

 methods to obtain desired results were tried. The first was to 

 tap the rat's snout gently with the forefinger of the right hand to 

 test the threshold for touch; the second was to press the snout 

 ventralward .and immediately release the pressure. This last 

 method was as close a reproduction of conditions which produce 

 the neck reflex to raise the latch as could be devised. Prac- 

 tically, the same results were obtained from both tests. There 

 was either a slight stiffening of the neck muscles, or a slight rais- 

 ing of the head dorsally, and in some cases to the midline of the 

 body before stiffening of the neck muscles occurred. Movement 

 of the head was less general than were contractions of the muscles 

 of the neck which resulted in the stiffening of the neck. Very 

 little coordination of the reflex movement of the neck with the 

 other body integrated reflexes was evoked; but rats that gave 

 any indication of an interaction of the neck reflex with other 

 body parts showed, when in the environment of the problem, 

 evidence of reflex excitability. 



The third test was productive of better results; the rat's head 

 was passively raised dorsally by placing the forefinger under 

 the lower jaw to a position approximately at a right angle with 

 the midline of the body. This test in many rats immediately 

 evoked remarkable reflexes. The number of them varied greatly 

 in rats and in some there was produced a coordination with 

 other groups of reflexes which were regarded as necessary for the 

 attainment of posture under the latch. Once more this coor- 

 dination was much more manifest in rats that showed a degree 

 of reflex excitability. When in rats interaction of other body 

 parts occurred with the production of integrated coordinated re- 

 flexes, a fair prediction was often made that posturing with the 

 raising of the latch of the latch-box problem would take place, 

 and in every case when the prediction was not fulfilled, reflex 

 excitability soon subsided. 



Just what the nature of these reflex disturbances was could not 

 at once be made out. They appeared to be native complex re- 



