54 SENSATION AND REACTION 







From the character of the typical sensory 

 organ a nerve ganglion to which two nerves are 

 attached, one for bringing stimuli of sensa- 

 tion, the other for carrying away impulses of 

 motion it would appear that the movement of 

 a muscle is the necessary and inevitable conse- 

 quence of the receipt of a sensory impression. 

 And there is reason to believe that this is so, and 

 that every impression is, so to speak, a starting 

 lever which releases muscular action. Experi- 

 ments with human subjects, in which the beating 

 of the heart, or the expansion of the lungs, is 

 carefully registered, indicate that sensory im- 

 pressions which, so far as consciousness can detect, 

 do not stimulate the least muscular reaction, 

 are, as a matter of fact, accompanied by it. 

 The sight of a red colour, for instance, is found 

 to quicken the motion of the heart in some per- 

 sons. We have then experimental warranty for 

 the expression " seeing red." 



A sensory impression that affects the brain, 

 and is not localized in the instinctive nerve sys- 

 tem that directs our internal mechanism, is, 

 however, rarely a single occurrence : it generally 

 sets free several impulses and a stream of memo- 

 ries that conflict with the impulse that is 

 primarily aroused, and, it may be, with one 

 another. A terrifying noise makes us start : 

 it would make us run were hurrying not in- 

 hibited by a feeling of shame, by a suspicion that 

 we might be meeting the danger, or by knowledge 

 that the noise as a matter ot fact meant no risk 

 to us. Hence, in the majority of cases, our 

 external behaviour is not guided by primary 

 instinctive reactions, but is the product of a 

 struggle between a number of impulses. Such 

 an arrangement is obviously inconsistent with 



