[6] Ether and chloroform, which are now exciting so much discussion among medical men, furnish a good illustration. The value of the discovery which has recently been made in regard to them, great as it undoubtedly is, cannot as yet be exactly ascertained. But the profession will be learning more and more in relation to them, and multiplied and extended observations will at length determine their precise value, and the circumstances which should govern us in their use. CHAPTER IV. QUACKERY. The reader is now prepared, by the facts and considerations presented in the previous chapters, to see in what way quackery, in its various forms, has obtained such a hold upon the community. If results in medical treatment could always be traced to their real cause, there would be no room for the arts of the empiric. But the reader has seen that, in the progress of every case of disease, there are many causes acting together in the development of results, and that many of these act secretly; and that there is, therefore, special need of caution in our conclusions, in regard to the operation of remedies. And yet, notwithstanding the manifest necessity for caution, there is no subject to which the ‘_post hoc propter hoc_’ mode of reasoning is so frequently, and so incautiously applied. It is the erroneous reference of effects to causes, consequent upon this mode of reasoning, which is the great source of quackery.[7] Let us see how this result is produced. Take any remedy, no matter what it is, whether it be positive in its character, or entirely inert, and it can be made to acquire an extensive reputation for curing disease. Suppose that it is of a positive character. Let quite a large number of persons in a community be persuaded to take it. It would be appropriate to a few out of the whole number of cases, just as a man firing into a crowd of men at random would be apt to hit some of them. Then there are some, who, through the recovering power of nature, get well while using the medicine, perhaps even in spite of it, and falsely attribute the cure to it. The _many_ that are not benefitted soon, give up the use of the remedy, and the fact that they have taken it is known to but few, and is soon forgotten even by them. But the few that _chance_ to derive benefit from it, or that are cured by nature while taking it, proclaim everywhere the virtues of the remedy with the ardent gratitude of restored health, and willingly give certificates of their cure for the benefit of suffering humanity. All this helps to get the new remedy in vogue in other places; and wherever it is introduced, the same result, for the most part, is realized. The consequence is, that the remedy comes into extensive use, and continues in the popular favor, till some other remedy, by the same process, supplants it.