2. Many of them are essentially, sometimes wholly, untrue. Some of this class are written by the local agents of the proprietor; and the individuals are persuaded to sign them, because the medicine had been gratuitously furnished, or for some other reason. I know many facts which I could adduce in proof of this statement. I will mention, however, but one case. One who had been an apothecary, and had sold large amounts of quack medicines, stated, that in one year he sold three thousand dollars’ worth of one medicine—that he had no satisfactory proof of its having cured a single case of disease—that he had obtained, however, many certificates of cure, but not one from any person who had paid for the medicine. 3. Another class of certificates are obtained in this way. Invalids are very apt, on taking a new medicine, to imagine themselves for a little time to be benefitted; but after a while they find that it is mere imagination. Many certificates are obtained of such persons at the time when they feel encouraged in regard to their prospect of recovery. The empiric understands that this is the golden opportunity for him, and he will have no delay if it can be avoided. It is astonishing what sensible people are sometimes caught in this way. A deaf gentleman once asked me my opinion of an empiric, who pretended to have uncommon skill in the cure of deafness. He found, among the published certificates, a letter from a gentleman of his acquaintance, of the highest standing both in character and intellect, expressing great gratitude for the relief which he had experienced from the practice of this ear doctor. He wrote to his friend a letter of inquiry. His friend replied, that when he returned from his visit to this quack, he thought himself to be somewhat better, and was so much delighted that he magnified the improvement in his imagination, and in this condition wrote that certificate; and that he was now satisfied that he unwittingly made in that certificate a really false representation of his case. 4. Another class of certificates come from those who are really relieved while using the medicines, in regard to which they certify. The inference, according to the ‘_post hoc propter hoc_’ mode of reasoning is, that the medicines, of course, cured them. I need not stop to show that this inference can by no means always be a correct one. I trust that the facts presented in the previous chapters are sufficient to satisfy the reader on this point.