INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 489 



method used. Sensory control of movements has never been 

 observed to be present. Both when the reflex mechanisms are 

 developed and undeveloped, progression once started by excita- 

 tions in the external senses, continues without further excitations 

 from these senses. 



Direct evidence is not wanting to show that the external 

 senses, in a definite w&y, direct progression and produce re- 

 sponses that solve a problem. There is evidence that stimuli 

 from different parts of the environment spread excitations in 

 the senses, increase the extensor tone of muscles for posture, 

 for progression, and for the production of definite movements 

 such as the extensor thrust to plunge the plane. Without the 

 facilitation of posture of some kind, the external senses cannot, 

 it appears, direct movements nor produce them. This increase 

 in extensor tone for posturing is facilitated by the development 

 of an interaction with other reflex body parts, such as that for 

 the production of reflex excitability and possibly other reflex 

 parts. In the inclined-plane problem, this development of 

 interaction of body parts for the attainment of posture, is observ- 

 able when the cumulative effect produced by all movements, in 

 particular when the plane is plunged, results in the improvement 

 of responses. At this time, the plunging of the plane produces 

 rapid responses, indicating a spread of excitations from the 

 internal and external senses. Rapid descent from the plane, 

 turning around, using the olfactory and visual senses show that 

 many senses and other body parts interact. Such an inter- 

 action is the beginning of the facilitation of posture for directive 

 integration and the performance of movements to plunge the 

 plane. In some instances rapid descent and progression from 

 the plane is stopped by the noise of the door opening. When 

 progression stops, the body is crouched and this position must 

 increase the interaction of body parts. The most that sense 

 functioning can be said to accomplish is to hasten the develop- 

 ment of interaction of parts, and this is again hastened when 

 reflex excitability is hypernormal, and retarded when it is hypo- 

 normal. Observations once more substantiate the view that 

 the sense organs function in no such exclusive manner in order 



PSYCHOBIOIXJOY, VOL. II, NO. 



