data under the guidance of the interests to which these principles give rise; and when the work proceeds with the confidence that, more indirectly but more surely, will the richest practical benefits thus accrue. The marked contrast exemplified in the history of chemistry and astronomy, and in a more limited way of brain physiology, make it proper to speak of the very different pursuits with which they were associated as their antecedents and not as early stages of their own development. Intimate as may be the relations between the two historically, the one represents but the forerunner of the other; it indicates in what direction interest guided thought before that changed interest appeared, which made possible the germination and growth of the true science. Only when the weeds had been rooted out did the flowers begin to thrive. I The history of hypnotism furnishes another and a varied illustration of a similar relation. If we accept as the essential fact of modern hypnotism the demonstration of an altered nervous and mental state, in which suggestibility is increased to a quite abnormal degree; in which, accordingly, functions not ordinarily under the control of voluntary effort become so controllable, and there are induced simple and complex modifications of physiological and psychological activities,--then the condition of opinion that prevailed prior to the recognition of the true significance of the phenomena in question, the false and unfounded and mystical conceptions concerning them, may properly be grouped together as the antecedents of hypnotism. The entire aspect of the problem under the one régime is strikingly different from its appearance under the reign of the successor. In the presentation, from the point of view of modern hypnotism, of the more important steps in the tortuous and laborious transition from unbridled speculation and fantastic practices to a rational and consistent body of truth, a twofold interest may be maintained; the one, in the fluctuation of opinion antecedent to the scientific recognition of hypnotism, and the other in the _dramatis personæ_ concerned in this history and their contributions, great and small, for good or for ill, to that gradual and irregular change of attitude the tested residue of which modern hypnotism embodies. The latter interest will form a helpful guide for selection among the complex sequence of events with which we shall have to deal. Accounts of the well-established phenomena of hypnotism are so readily accessible, that it seems sufficient to emphasize these two fundamental points--the ultimate recognition of an altered psycho-physiological state, and of the dominant part which suggestion plays in the development of hypnotic phenomena--and to accept them as furnishing the principles according to which the survey of the antecedents of hypnotism is to be conducted.