676 COMPARATIVE ELECTRO-PHYSIOLOGY 



also seen, the masked positive component, and from the point 

 of view of energy, they represent the algebraical summation of 

 income and expenditure, positive and negative, increase and 

 diminution. Considered as sensation, then, this particular 

 effect will be composed of dual elements, a mixture of positive 

 and negative tones. With very strong stimulation, finally, 

 the negative effect will be very great ; expenditure will be 

 greater than income ; and the sensation will assume a pre- 

 dominantly and persistently negative tone. 



The complex negative, moreover, containing a masked 

 positive, is capable of dissociation into its component 

 elements. By the partial or complete block of conductivity, 

 it is exhibited as dual response of 'dissociation,' or by the 

 total suppression of the negative, as positive alone. In this 

 way, a sensation, originally painful, may be rendered not 

 unpleasurable, or even pleasurable. It was further shown, 

 employing electrotonus and the sensimeter, that an indif- 

 ferent and semi-fused tone of sensation can, by merely exalting 

 the excitability of the tissue, be converted at will into one 

 which is continuous and painful. By depressing the excit- 

 ability, on the other hand, this indifferent sensation may be 

 made pleasurable and strikingly discrete. 



