NATURE OF SENSE ORGANS 17 



pulse that, after passage through the central nervous 

 organs, results in action. 



From the beginning many reflexes were believed to be 

 unassociated with consciousness and though this view was 

 subsequently combated and the idea of the reflex extended 

 to nervous operations that included an obvious sensa- 

 tional element, it nevertheless remained true that a host 

 of reflex operations could be pointed out that were with- 

 out representation in consciousness. Thus the impulses 

 that flow from the vestibular portion of the human ear 

 and that are of the utmost importance in maintaining 

 equilibrium provoke no obvious sensations and the vast 

 flux of afferent nerve action that moves from the mus- 

 cle to the spinal cord and that is so essential to the 

 coordination of bodily movements, runs its course without 

 exciting sensation. These and many like instances have 

 made it clear that the reflex, even in the most special ap- 

 plication of the term may as often be unassociated with 

 sensation as associated with it. 



As the first step in every reflex is the excitation of a 

 sense organ and as many reflexes are unassociated with 

 consciousness, it must be admitted that sense organs, not- 

 withstanding the name, are not always necessarily con- 

 cerned with sensations. Many certainly have nothing 

 whatever to do with such central nervous states. Thus 

 it is doubtful if the normal activity of the sensory endings 

 in our muscles and tendons is ever productive of sensation. 

 In consequence of this condition a reasonable objection 

 was raised to the term sense organ and it was proposed by 

 Bethe (1897) to use in place of it the word receptor. 

 Although the theoretic force of this objection has not 

 always carried conviction, the term receptor has come into 



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