DISSOCIATION OF COMPLEX SENSATION 673 



In investigating the influence of alcohol (p. 493) we saw 

 that three distinct effects were induced by it on the 

 receptivity, responsivity, and conductivity of a tissue 

 respectively, these effects themselves being further modifiable 

 by the duration and intensity of the application. It was 

 shown that, in the first stage of its application, alcohol exalted 

 the power of receptivity. But its effect on conductivity and 

 responsivity, especially after a certain duration of application, 

 was one of great depression. The total effect of alcohol is 

 thus somewhat complex. At an early stage of its applica- 

 tion there is an effect of exaltation. After a while, however, 

 the conducting power becomes increasingly depressed by its 

 action. This means that the passage of the true excitatory 

 or negative wave is progressively impeded or even blocked, 

 the positive alone continuing to be transmitted for a time. 

 At a certain stage of alcoholisation, therefore, the negative 

 tone of an existing sensation, normally painful, will, as it 

 were, be erased. And this withdrawal of the painful element, 

 by causing sudden relief, together with the actual trans- 

 mission of the positive wave, may induce a tone of sensation 

 which might even perhaps be regarded as pleasurable. In 

 any case the abolition of conductivity must eliminate the 

 element of pain, and it was undoubtedly this which, in 

 pre-anaesthetic medicine, caused its employment for certain 

 minor operations. Long and intense alcoholisation will, of 

 course, obliterate all sensation. On the after-effects of so 

 depressing a reagent it is unnecessary to dilate. 



Effects, in some respects parallel, may be observed under 

 etherisation, where, at a certain stage in the action of the 

 narcotic, there is a cessation, not of all sensation, but of its 

 painful element alone. Thus, by depression of conductivity, 

 and consequent suppression of the negative wave, the positive 

 may be ' dissociated ' from the negative sensation. Sustained 

 pressure on a nerve is also known to depress conductivity, 

 and it is interesting to note here that pressure on the ulnar 

 nerve-trunk will abolish painful sensation, the positive, or 

 mere contact-sensibility remaining practically undiminished. 



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