Page:Philosophical Review Volume 1.djvu/444

contract while others expand under the same changes of temperature. From their work and from some late experiments of our own with different drugs injected into the skin, we are led to believe that the heat nerves of Goldscheider end in one kind of tissue having one characteristic of temperature contraction, and the cold nerves in another tissue having the opposite characteristic. Also, it would seem that the heat tissues are actively contracting when the cold tissues are either passive or actively expanding, and that the cold tissues are actively contracting only when the heat tissues are passive or expanding. Also, each of these tissues has its range of temperature activity, and each range is complementary to, and exclusive of the other. This will be understood if it be recalled that a common gum band is only actively elastic within a certain range of temperature; if too hot the gum melts, if too cold it is stiff. All this being so, we may easily conceive why our heat and cold sensations from the same area are mutually complementary and exclusive of each other. If now we assume, by way of hypothesis, that both pain and pleasure nerves also end in each of these kinds of tissue, and that each kind of such nerves is susceptible to a peculiar intensive range of stimulation, we may form an idea of how our common temperature comforts and discomforts may be explained thereby. We have indicated certain biological reasons why pain should with benefit respond peculiarly to unusually vigorous stimulations, and why pleasure throughout the various senses should develop in a scale of intensities for the organs of each sense proportionally to the intensities of the forms of stimulation proper to such organs. Indeed it is a proper answer to the question, Why in any particular place or function is a certain sense developed to or limited to any certain range of intensity? to answer, Because it was most needed and most beneficial in that particular place and function that it should be developed to that particular degree and range of intensity. It may be easily understood, then, how pain having developed to warn against too intense temperatures, and pleasure having developed to prompt to certain conduct best suitable to certain moderate degrees of temperature, that they should thus have