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 through the involuntary life—the mind of the subject acting on the body—and producing results which, it is to be noted, are as decided, as uniform, and as permanent as when produced by powerful objective influences. This element of error slips into all the ordinary experiments with new remedies and supposed new forces in the animal body, thus corrupting science at its very sources. The neglect of this element of error would of itself, even though all the other errors were guarded against, destroy entirely the scientific value of all such experiments, for example, as those of the committees of the French Academy with clairvoyants and mesmerism; it is because physicians of experience instinctively feel this element of error, that reports of cases wrought by novel and strange and especially by imposing methods of treatment are so frequently discredited. Under this head come also all the so-styled miracles of healing, whatever may be the paraphernalia through which they are accomplished.

I know not where can be found a better single illustration of the effect of this element of error, alone of itself, in scientific research, when all the other elements of error seem to be provided for, than in the experiments on animal magnetism of the late Dr. J. K. Mitchell, as recorded in the volume of his miscellaneous writings. Dr. Mitchell was an original thinker, an observer of patience and care, and a clear and logical writer, who suggested more than he told, and his chapter on animal magnetism was incomparably the best essay ever written on that subject down to the date of its publication. This paper—which consisted of a record of independent, careful, and many times repeated experiments on living human beings, with remarks thereon—shows that the author not only had the courage and the power to do his own thinking and experimenting, but that he recognized some of the chances of error in experiments of this kind, and fortified himself against them; while of the errors that enter through the doors of the involuntary life—the unconscious deception of the subject experimented on—he knew, and apparently suspected, little. His essay is therefore at once a model and a warning: a model for thoroughness and precision up to a certain point, or within a limited area; a warning as demonstrating the worthlessness of all experiments with human beings when any one or two of the six sources of mistake are overlooked. So accurate and scientific were these experiments, in certain directions, that they have furnished an important contribution to our knowledge of some of the symptoms of mesmerism, in spite of the fact that the author failed, like hundreds of able men in science before him, to solve the problem of the nature of trance. By not understanding and taking into account the phenomena of the involuntary life, of which in his day very little was known, and of trance, of which nothing was known, this acute and philosophic observer allowed the subjects on whom he operated to constantly deceive themselves and deceive him, and to drive him to the logical but absolutely false conclusion that the mesmeric trance was an