Sentence:  Hereby , the external object viewed by the eyes remains the thing that is seen , not the retinal image , the purpose of which would be to achieve perceptive cooperation by stirring sympathetic impulses in the other <WSD>sensory</WSD> centers , motor tensions , associated word symbols , and consciousness . 
Meaning of the word marked with <WSD> tags:  of a nerve fiber or impulse originating outside and passing toward the central nervous system