THE ASSOCIATION OF IDEAS 45 



The stimuli in the several cases, we may suppose to be the 

 words "right," "left," and "over," addressed to the pupil's audi- 

 tory receptors; or may be significant movements of the instruc- 

 tor's hands affecting the visual receptors; or tactual stimuli ap- 

 plied by the instructor's hands; or combinations of these. As 

 learning progresses, ideational rather than perceptual processes 

 become increasingly important, but these, too, depend on stimuli 

 of the receptors of some sense, or senses, hence we may designate 

 the total stimulations in the three reactions as A, B, and C, and 

 designate the corresponding processes in the receptors of the 

 senses involved as A', B', and C'. 



The muscular contractions (and relaxations) in the three reac- 

 tions may be represented, as if there were only one muscle-cell 

 involved in each, by a, &, and c. 



Changes in the muscles in contraction a, stimulate the recep- 

 tors in the muscle spindles with which all striped muscle is pro- 

 vided. Afferent current from a', the process in the muscle-recep- 

 tors, is thus sent into the "centers" (spinal cord and brain), 

 reissuing, in accordance with habits already established, over some 

 efferent route (not represented in Fig. 1) and thus forming a new 

 neural circuit, the transit over which conditions the consciousness 

 of the leg movement. In the early stages of learning this transit 

 may dominate the integration of the total nervous system for 

 the moment, giving rise to vivid (attentive) consciousness of the 

 movement. By degrees this dominating tendency of the transit 

 disappears, until finally this particular transit is so completely 

 absorbed in the integrations dominated by other transits that 

 there is practically no consciousness of the leg movement as a 

 distinct entity. 



Since the transit beginning with A' has a certain duration, and 

 its individual function is brief, its residual activity is "drained" 

 into the circuit of the next important transit, B'-b. By the con- 

 cept of "drainage" above assumed, we mean at this time nothing 

 more than that a functional connection is established between the 

 arc commencing with a' and the new arc B'-b. It may be true 

 that in the establishment of this connection "current" already 

 flowing over the a' arc is actually diverted to the B'-b circuit 



