In all these methods the operator is usually blindfolded, so that he may get no assistance from any other source than the unconscious muscular action of the subject.
The movements of the operator in these experiments may be either very slow, cautious, and deliberate, or rapid and reckless. Brown, in his public exhibitions, was very careful about getting the physical connection right, and then moved off very rapidly, sometimes in the right direction, sometimes in the wrong one, but frequently with such speed as to inconvenience the subject on whom he was operating. These rapid movements give greater brilliancy to public experiments and serve to entrance audiences, but they are not essential to success. They serve, no doubt, in many cases, to bewilder or partially entrance the subject, and thus to render him far more likely to be unconscious of his own muscular tension and relaxation through which the operator is guided.
The power of muscle-reading depends mainly, if not entirely, on some phase of the sense of touch. Dr. Hanbury Smith tells me that a certain maker of lancets in London had acquired great reputation for the superiority of his workmanship. Suddenly, there was a falling off in the character of the instrument that he sent out, and it was found that his wife, on whom he had depended to test the sharpness of the edge on her finder or thumb, had recently died.
That the blind acquire great delicacy of touch has long been known; Laura Bridgman is a familiar illustration. Dr. Carpenter states (although there are always elements of error through the unconscious assistance of other senses in cases of this kind) that Miss Bridgman recognized his brother, whom she had not met for a year, by the touch of the hand alone.
Every physician recognizes the fact of this difference of susceptibility to touch; and, in the diagnosis of certain conditions of disease, much depends on the tactus eruditus. I am not sure whether this delicacy of perception, by which muscle-reading is accomplished, is the ordinary sense of touch, that of contact, or of some of the special modifications of this sense. It is to physiologists and students of diseases of the nervous system a well-known fact that there are several varieties of sensibility—to touch, to temperature, to pressure or weight, and to pain—which, possibly, represent different rates or modes of vibration of the nerve-force.
The proportion of persons who can succeed in muscle-reading, by the methods here described, is likewise a natural subject of inquiry. Judging from the fact that, out of the comparatively few who have made any efforts in this direction, a large number have succeeded after very little practice, and some few, who have given the matter close attention, have acquired great proficiency, it is probable that the majority of people of either sex, between the ages of fifteen and fifty, could attain, if they chose to labor for it, under suitable