This last edition has received so many additions and alterations, as might almost entitle it to the character of a new performance.----A stiffness of opinion has been but too commonly observed, especially among writers on science; and age has been seldom found to have worn out this pertinacity: a favourite hypothesis has been defended even in opposition to the most obvious experiments, with a degree of obstinacy ever incompatible with the real interests of truth. On the contrary, our ingenious author has set before his literary successors, an example of sagacity and fortitude, truely worthy of imitation, in the victory he obtained over these self-sufficient pre-possessions; length of years was so far from rivetting in him an inflexibility of sentiment, that, joined to a most extended experience, it served only to teach him, that he had been mistaken: his candid retraction of what he thought to have been advanced amiss by himself, cannot be better expressed than in his own words. “Neither have I, says he,[3] been ashamed on some occasions, (as the Latins said) _cædere vineta mea_, to retrench or alter whatever I judged to be wrong. _Dies diem docet._ I think truth never comes so well recommended, as from one who owns his error: and it is allowed that our first master never shewed more wisdom and greatness of mind, then in confessing his mistake, in taking a fracture of a skull, for the natural suture;[4] and the compliment, which Celsus[5] makes to him on this occasion, is very remarkable and just;” nor is it less applicable to Dr. Mead at present than it was to the Coan sage in his day. “_More scilicet_, inquit, _magnorum virorum, & fiduciam magnarum rerum habentium. Nam levia ingenia, quia nihil habent, nihil sibi detrahunt: magno ingenio, multaque nihilominus habituro, convenit etiam simplex veri erroris confessio; præcipueque in eo ministerio, quod utilitatis causâ posteris traditur._” [3] Advertisement prefixed to the last edition of the essay on poisons, p. 4. [4] Epidem. lib. iv. § 14. [5] Medicin. lib. viii. c. 4.