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"Touch," "itch," "pain," "tickle"—these words conjure up in our minds a spectrum of every day sensations which seem so simple as to be almost ridiculous, but they have proved well-nigh incorrigible in all efforts to make a definitive analysis of them. The experimenter is perforce doubly blind. The experimenter as subject chooses words to describe his reactions which inevitably are incomplete, if not misleading, and experiments in animals have the further barrier that they must be interpreted in terms of the animal's response rather than a descrip- tion of what is being felt. Thus, despite the fact that there are marvelous recording devices for measuring the faint impulses which dart along tiny nerves or slivers of nerves, the equating of electrical current with sensation has proved far too complex to yield broad generalization. Nonetheless, much progress has been made in the past two decades in the area of clinical investigation