SENSATION 



energy. The living substance at rest, which is sensitive 

 or irritable, is in a state of equilibrium and indifTerence 

 to its environment. But the active plasm, that receives 

 and feels a stimulus, has its equilibrium disturbed, and 

 corresponds to the change in its environment and its 

 internal condition. This response of the organism to a 

 stimulus is called "reaction" — a term that is also used 

 (in the same sense) in chemistry to express the inter- 

 action of bodies on each other. At each stimulation the 

 virtual energy of the plasm (sensitiveness) is converted 

 into living or kinetic force (sensation). The share of the 

 stimulus in this conversion is described as a "release" 

 of energy. 



The term "reaction" stands in general for the change 

 which any body experiences from the action of an- 

 other body. Thus, for instance, to take the simplest 

 case, the interaction of two substances in chemistry is 

 called a reaction. In chemical analysis the word is used 

 in a narrower sense to denote that action of one body 

 on another which serves to reveal its nature. Even 

 here we must assume that the two bodies feel their 

 different characters ; otherwise they could not act on each 

 other. Hence every chemist speaks of a more or less 

 "sensitive reaction." But this process is not different 

 in principle from the reaction of the living organism to 

 outer stimuli, whatever be their chemical or physical 

 nature. And there is no more essential difference in 

 psychological reaction, which is always bound up with 

 corresponding changes in the psychoplasm, and so with 

 a chemical conversion of energy. In this case, however, 

 the process of reaction is much more complicated, and 

 we can distinguish several parts or phases of it: i, the 

 outer excitation; 2, the reaction of the sense-organ; 

 3, the conducting of the modified impression to the 

 central organ; 4, the internal sensation of the conducted 

 impression; and, 5, consciousness of the impression. 



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