produced artificially or by disease, to find one sense obliterated (e.g. that of heat or cold) whilst another is not cut off (e.g. that of touch or pressure): the only marked characteristic in this case is this, that the sense which is cut off is not clearly differentiated in consciousness until it appears under the conditions which make its phase painful.
5. The facts which lead to the conclusion as to there being a separate pain path in the spinal cord are explicable in a manner so similar that repetition of the counter-argument seems unnecessary.
6. The argument based upon the claim of the discovery of specific pain nerves deals with evidence so distinctly in dispute that I do not feel that it needs reply here. I have already shown the direction in which I think it probable the reinterpretation of observations will be made, and if my surmise be correct these observations would not be in opposition to my theory.
7. Is it possible under our theory to explain the distribution of pleasures and pains as we find them? I think it is as simple as under the sensational theory.
Pleasure, under our hypothesis, involves a tendency to continuance of the activity which is producing the pleasure; and pain, a tendency to discontinuance of the activity which is producing the pain.
It is evident that, under the laws of elimination of the unfit and of survival, those individuals would prevail whose capacity to use stored force in reaction to a stimulus (or, in other words, whose pleasure-getting) was confined to organs producing activities the continuance of which would be advantageous to the individual.
Again, those would have the advantage whose tendencies to discontinuance of special activities (or, in other words, whose pain-gettings) were limited to organs producing activities which would be disadvantageous to the individual if continued. In general, then, we should expect to find pleasure capacity emphasized in directions in which continuance of the activity will be advantageous to the individual and pain production prompt (pleasure capacity practically absent) where the continuance of
