Sydenham is justly celebrated for the happiness of his descriptions, and his skilful application of simple methods of cure, which are as effectual as they were novel in that age when a medical prescription sometimes contained a hundred different substances; but he has merit of a higher kind, as a discoverer of general laws. Among others, he was the first to notice that there is a uniformity in the fevers prevailing at any one time, which is subject to periodical changes; and that other acute diseases often partake largely of the same general character, and sometimes even merge in it altogether, as the plague is said to have swallowed up all other diseases. This, which he ascribed to some peculiar state of the atmosphere, he called its epidemic constitution; and to be aware of its vicissitudes must of course be very important to the physician as a guide to practice. The value of these laws, which Sydenham deduced from a multitude of observations, has been attested by almost every medical writer since his time. His works have been repeatedly printed in the original Latin, as well as in English and the continental languages. The first was published after he had been sixteen years in practice; the last he edited himself, is dated three years before his death; and an elegant compendium of his experience was published posthumously by his son. They all appear to have been extorted by the importunity of his friends or the misrepresentations of his enemies. It is said that they were composed in English, and translated into Latin by his friends Mapletoft and Havers: there is, however, little reason for attaching credit to this report, as we are assured, on the authority of Sir Hans Sloane, who knew him well, that Sydenham was an excellent classical scholar, and perfectly capable of expressing himself elegantly in Latin. They are most carefully written and clearly expressed, and bear marks of the utmost truth and impartiality in the narration of facts, and judgment in arranging them. They are not voluminous, as he studiously refrained from overloading them with trivial matter, and from entering into the detail of a greater number of cases than might be sufficient to illustrate his method of practice. His object was to confine himself to the results of his own observation: to this he pretty strictly adhered, so that little space is occupied in his writings by quotations or criticism. It must be admitted that he occasionally lapses into theoretical discussion, in violation of his own principles; but as he seldom or never permitted his fancy to divert him from what was practically useful, he may be pardoned, if in that age of speculation he could not entirely resist the seduction. A graver charge against him is, that he overlooked or undervalued the immense body of information to be obtained from examining the effects of diseased actions after death, and devoted himself too exclusively to the