The quack aware of the prevalence of this superficial knowledge of medicine, gathered from popular books and lectures, often makes provision for the taste thus engendered. He hires some one, perhaps a medical student, to prepare for him a disquisition on some of the principles of medical science, which is to accompany the certificates setting forth the virtues of his nostrums. This disquisition may all be correct, though it is more commonly a mixture of truth and fallacy, so combined, that the superficial reader does not separate the one from the other. It answers the purpose for which it is intended. It convinces most people who read it, that the author (whom they suppose to be the proprietor of the medicines) really has a great knowledge of medical science, and that, therefore, though other patent medicines may be impositions, his cannot be. There is often in these disquisitions page after page of physiological discussions, in learned guise, which have no sort of bearing upon the nature of the medicines recommended, though they do have most manifestly upon their _sale_, as the result shows. Let me not be understood to mean, that none but physicians ought to know anything about the human system; nor that the knowledge of it, which is obtained from popular books and lectures, can be of no advantage in the warfare with empiricism. Though, when it is relied upon as the chief, almost the only, weapon in this warfare, it is, as you have seen, of little avail, and is often even turned against the cause of truth and science; yet, as an _adjuvant_ to other means in removing quackery, it may prove very valuable. What then, let us enquire, are those other means? I have shown in another chapter, that the principal popular errors in medicine arise from partial views of the operations of disease and the effects of remedies, and are false conclusions in regard to the relation of cause and effect. These false conclusions are, as you have seen, the basis of quackery; and therefore one of the chief means of removing quackery is to be found in the exposure of the fallacy of these conclusions.