The forms which quackery assumes are endless; but the material out of which they are evolved is essentially the same in all ages and in all countries. There are certain medical errors which are common to man everywhere and in every condition. It is these which constitute the material of quackery, whether it appear among the savage or the civilized, the rude or the refined, the illiterate or the learned. One object of this book is to develop these fundamental errors, and to show the _modus operandi_ by which the genius of imposture has produced from them the fantastic and ever-changing shapes of empiricism.[1] I notice particularly some of the specific forms of quackery which are now prevalent, not because they differ essentially from those which have preceded them, but because they have a _present_ interest to the reader. One of the objects at which I aim is to expose to the public the fallacy of those sources of evidence, upon which they rely in estimating the comparative merits of physicians, and to show them what tests they have at command, which will not prove fallacious. The proper use of these tests would save the public from mistaking, as they now often do, the plausible pretensions of the superficial practitioner, and the charlatan, for the evidences of real skill and wisdom. Another object will be to present the claims of the medical profession to the respect and the confidence of the community. As it now is, the profession stands in a somewhat false position before the public. The grounds upon which we ask their regard and trust are not generally understood. The confidence which is reposed in us is not as intelligent as it should be. It is unsettled and capricious. It is overweening at one time, and it is entirely withheld at another, and for the most frivolous reasons. The inconsistencies of even the well informed on this subject are surprising. Many, who on some occasions confide implicitly in nothing but educated science, are found at other times submitting themselves and their families to the haphazard administrations of empiricism. But while I attempt to establish the claims of the medical profession to the confidence of the people, and to defend it against the aspersions which are unjustly cast upon it, I endeavor to exhibit faithfully the abuses which exist in the profession itself. The quackery which is practised among medical men is a much greater evil than that which is abroad in the community. I attack it therefore with an unsparing hand. In so doing I expose many of the tricks and manœuvres which are employed by those physicians, who, pursuing medicine as a _trade_ instead of a profession, study the science of patient-getting to the neglect of the science of patient-curing. When the rules of an honorable professional intercourse shall come to be properly understood and appreciated by the public, one of the great sources of the success of quackery will be removed.