The new treatise at once attracted attention, and was reviewed in the Philosophical Transactions for 1666. In the same year there appeared a Dutch edition of the Method. The value and the effect of this treatise we can scarcely fully appreciate at the present time, but its pith is well given by Dr. John Brown, author of the “Horæ Subsecivæ.” “Besides their broad, accurate, vivid delineations of disease—portraits drawn to the life, and by a great master—and their wise, simple, rational rules for treatment, active and negative, general and specific—there are two great principles continually referred to as supreme in the art of medicine. The first is that nature cures diseases; that there is a recuperative and curative power, the _vis medicatrix_, in every living organism, implanted in it by the Almighty, and that it is by careful reverential scrutiny of this law of restoration that all our attempts at cure are to be guided; that we are its ministers and interpreters, and neither more nor less; and the second, that symptoms are the language of a suffering and disordered and endangered body, which it is the duty of the physician to listen to, and as far as he can to explain and satisfy, and that, like all other languages, it must be studied. This is what he calls the natural history of diseases.... What Locke did for the science of mind, what Harvey and Newton did for the sciences of organic and inorganic matter, Sydenham did for the art of healing and of keeping men whole: he made it in the main observational; he founded it upon what he himself calls downright matter of fact, and did this not by unfolding a system of doctrines or raising up a scaffolding of theory, but by pointing to a road, by exhibiting a method—and moreover teaching this by example, not less than by precept—walking in the road, not acting merely as a finger-post, and showing himself to be throughout a true artsman and master of his tools. The value he puts upon sheer, steady, honest observation, as the one initial act and process of all true science of nature, is most remarkable; and he gives himself, in his descriptions of disease in general and of particular cases, proofs quite exquisite of his own powers of persevering, minute, truthful scrutiny.” In 1668 a second edition of the Method was published, with additions, especially a chapter on the Plague, and prefaced by a eulogistic address in Latin verse, extending to fifty-four lines, by the illustrious Locke. In 1676 appeared the third edition of the Method, so much enlarged that it is better regarded as the first edition of the “Medical Observations.” In the same year Sydenham proceeded to the degree of Doctor of Medicine, not at Oxford, but at Cambridge, this choice being probably due to the fact that his son had entered at Pembroke College, Cambridge, two years before.