at first disagreeable to him, may eat a few with his dinner every day for years and always with enjoyment; but if he double his allowance some day, he will find the last one disagreeable. The man who walks little may find the action of his muscles on a five-mile walk very painful, but if he persevere he may come to find that definite amount of action in those muscles enjoyable and regularly required for his comfort. If, some day, however, he use these muscles in a twenty-mile walk, he will find that his capacity for pain in them has not disappeared. The hypothetical pain nerves have not become in the least disabled by disuse. How does it happen that for year after year we live on with practically no consciousness whatever of the existence of our intestines, until some day an irritant gives us excruciating pain? Have these supposititious pain nerves been lying dormant for so long, and yet actually gaining capacity to act with vigor, instead of becoming atrophied as other organs do?
Cases like this and the one immediately preceding it have led to the suggestion that a certain width of stimulation may be necessary to bring the pain nerves into action. If we accept this notion, we are confronted with the further difficulty that those of our activities which occur after rest are most vivid and widely effective, and yet are our most pleasurable experiences. The very same conditions which are held to bring about the stimulation of pain nerves here seem to be productive of pleasure. How is it that the man who is well-rested and vigorous in health finds it difficult to experience pain, although he is more active than the average man? How is it, on the other hand, that the gentlest stimulus is painful to one who is exhausted by illness or who is thoroughly weary?
So much for pain. What can be the special conditions which determine the stimulation of the supposititious pleasure nerves has not yet, I believe, been even suggested.
16. It would seem that if pain nerves are so widely distributed as is implied by the sensational theory, there should be a more distinct localization of pains than is experienced; this localization, in general, however, is so very indistinct that the fact has been used to argue for that theory which makes
