lute change of temperature would not feel the same when previously we had been growing warmer as when we had been growing colder. Pleasant coolness from a sudden fall of very high thermometer, and pleasant warmth from a sudden rise from very low thermometer, would be effects of summation. All this about temperature we present tentatively — to be placed on a footing with Hering's theory of color, as most plausible for the present. We would be positive of nothing except that it is more plausible than qualia. Finally, we make the same reservations about temperature as about sight, sound, taste, and smell. There may be no æsthetic sensations of temperature at all and no nerves. Our doctrine of specific pleasure and pain energies would not be wrecked without them. If they exist, the majority of temperature æsthetics are yet associations, and they may all be associations.
Touch should receive more consideration than our space affords, for here we find our most certain evidence of pleasure sensations. Sexual sensations under normal conditions can scarcely be doubted. Some local strokings, scratchings, and ticklings of the skin appear to be more or less constantly agreeable or disagreeable for most people; in certain diseases of the skin these phenomena are yet more markedly agreeable. By some authorities the tickle sense has been expected to prove the very foundation of the pleasure sense. We dissent from this view, but incline to believe that pleasure nerves may yet be discovered in certain regions of the skin.
An important and perhaps special class of sensations comes from the joints, but investigation of these has not yet reached the question of their æsthetics.
The distinction between muscle sense and sense of innervation is now familiar to psychology. As to direct pleasure from the muscles we are in the same doubt as elsewhere. It seems certain that single contractions are ordinarily indifferent. If certain obscure and summative conditions give us normal æsthetic sensations from the muscles, our theory will have room for them. As the relations which muscular activities and the psychic activities of their occurrence bear to the origin and
