HISTORY.] part in the vital processes. Chemical disturbances of these processes, called acridities, &c., were the cause of fevers and other diseases. Sometimes acid sometimes alkaline properties predominated in the juices and secretions of the body, and produced corresponding disturbances. In nervous diseases disturbances of the vital " spirits were most important. Still in some parts of his system Sylvius shows an anxiety to base hLs pathology on anatomical changes. The remedies he employed were partly Galenical, partly chemical. He was very moderate in the use of bleeding. The doctrines of Sylvius became widely spread in Holland and Germany less so in France and Italy. In England they were not generally accepted, till adopted with some modifications by Thomas Willis the great anatomist (1622-75), who is the chief English representa tive of the chemical school. Willis was as thorough-going a chemist as Sylvius. He regarded all bodies, organic and inorganic, as composed of the three elements spirit, sulphur, and salt, the first being only found abundantly in anim.il bodies. The " intestine movement of particles " in every body, or fermentation, was the explanation of many of the processes of life and disease. The sensible properties and physical alterations of animal fluids and solids depended upon different proportions, movements, and com binations of these particles. The elaborate work Pharma- ceutice Rationalis, based on these materials, had much influence in its time, though it was soon forgotten. But some parts of Willis s works, such as his descriptions of nervous diseases, and his account (the earliest) of diabetes, are classical contributions to scientific medicine. In the application of chemistry to the examination of secretions Willis made some important steps. The chemical school met with violent opposition, partly from the adherents of the ancient medicine, partly from the iatro-mechanical school. Towards the end of the 17th century appeared an English medical reformer who sided with none of these schools, but may be said in some respects to have sur passed and dispensed with them. Sydenham and Locke. Thomas Sydenham (1624-89) was educated at Oxford and at Montpellier. He was well acquainted with the works of the ancient physicians, and probably fairly so with chemistry. Of his knowledge of anatomy nothing definite can be said, as he seldom refers to it. His main avowed principle was to do without hypothesis, and study the actual diseases in an unbiassed manner. As his model in medical methods, Sydenham repeatedly and pointedly refers to Hippocrates, and he has not unfairly been called the English Hippocrates. He resembled his Greek master in the high value he set on the study of the " natural history of disease " ; in the importance he attached to epidemic constitution, that is, to the influence of weather and other natural causes in modifying disease; and further in his conception of the healing power of nature in disease, a doctrine which he even expanded beyond the teaching of Hippocrates. According to Sydenham, a disease is nothing more than an effort of nature to restore the health of the patient by the elimination of the morbific matter. The extent to which his practice was influenced by this and other a priori conceptions prevents us from classing Sydenham as a pure empiric, but he had the rare merit of never permitting himself to be enslaved even by his own theories. Still less was his mind warped by either of the two great systems, the classical and the chemical, which then divided the medical world. Sydenham s influence on European medicine was very great. His principles were welcomed as a return to nature by those who were weary of theoretical disputes. He introduced a milder and better way of treating fevers, especially small-pox, and gave strong support to the use of specific medicines, especially Peruvian bark. He was 811 an advocate of bleeding, and often carried it to excess. Another important point in Sydenham s doctrine is his clear recognition of many diseases as being what would be now called specific, and not due merely to an alteration in ths primary qualities or humours of the older schools. From this springs his high appreciation of specific medicines. One name should always be mentioned along with Sydenham that of his friend John Locke. The great sensational philosopher was a thoroughly trained physi cian, and practised privately. He shared and defended many of Sydenham s principles, and in the few medical observations he has left shows himself to be even more thorough-going than the "English Hippocrates." It is deeply to be regretted in the interests of medicine that he did not write more. It is, however, reasonable to suppose that his commanding intellect often makes itself felt in the words of Sydenham. One sentence of Locke s in a letter to W. Molyneux sums up the practical side of Sydenham s teaching. " You cannot imagine how far a little observation carefully miulo by a man not tied up to the four humours [Galen], or sal, sulphur. and mercury [Paracelsus], or to acid and alcali [Sylvius and Willis] which has of late prevaile l, will carry a man in the curing of diseases though very stubborn and dangerous ; and that with very little and common things, and almost no medicine at all." We thus see*that, while the great anatomists, physicists, and chemists, men of the type of Willis, Borelli, and Boyle, were laying foundations which were later on built up into the fabric of scientific medicine, little good was done by the premature application of their half-understood prin ciples to practice. The reform of practical medicine was effected by men who aimed at, and partly succeeded in, rejecting all hypothesis and returning to the unbiassed study of natural processes, as shown in health and disease. Sydenham showed that thess processes might be profit ably studied and dealt with without explaining them ; and, by turning men s minds away from explanations and fixing them on facts, he enriched medicine with a method more fruitful than any discoveries in detail. From this time forth the reign of canonical authority in medicine was at an end, though the dogmatic spirit long survived. The 18th century. The medicine of the 18th century is notable, like that of the latter part of the 17th, fur the striving after complete theoretical systems. The influence of the iatro-physical school was by no means exhausted ; and in England, especially through the indirect influence of Newton s great astronomical generalizations, it took on a mathematical aspect, and is sometimes known as iatro- mathemricical. This phase is most clearly developed in Fit- cairn (1652-1713), who, though a determined opponent of metaphysical explanations, and of the chemical doctrines, gave to his own rude mechanical explanations of life and disease almost the dogmatic completeness of a theological system. His countryman and pupil, George Cheyne, who lived some years at Bath, published a new theory of fevers on the mechanical system, which had a great reputation. Their English contemporaries and successors, Freind, Cole, and Mead> leaned also to mechanical explanations, but with a distrust of systematic theoretical completeness, which was perhaps partly a national characteristic, partly the result of the teaching of Sydeuham and Locke. Freind (1675- 1728) in his Emmenologia gave a mechanical explanation of the phenomena of menstruation. He is also one of the most distinguished writers on the history of medicine. Cole (see above) published mechanical hypotheses concern ing the causation of fevers which closely agree with those of the Italian iatro-mechanical school. More distinguished in his own day than any of these was Fuchard Mead (1673-1754), one of the most accomplished and socially successful physicians of modern times. Mead was the
pupil of the equally popular and successful John Radcliffo