PREVENTIVE MEDICINE. The prevention of disease is the true idedl of medicine. Its application is twofold—the pre ventive medicine of the community which is generally termed Public Health or State Medicine, and the prevention of disease or its sequelae in the individual.
The practice of preventive medicine had its origin in the ancient world. Hippocrates classified the causes of disease into those concerned with seasons, climates and ex ternal conditions, and those more personal causes such as irregular food, exercise and habits of the individual. Through the Middle Ages the principles of preventive medicine were ignored, in spite of the scourges of leprosy and plague. Then with the Renaissance came the new learning on the nature both of health and disease, which revolutionised the whole content of medicine and gave it a fresh centre of gravity and a new outlook. Leonardo da Vinci —whose genius suggested some of the great discoveries of modern science—and Vesalius of Padua, were followed in the
cen tury by Galileo, Harvey—who discovered the circulation of the blood—Helmont and the experimentalists, and Sydenham and the great practitioners who with their contemporaries observed the relation of the seasons, of telluric conditions, and the contagion in relation to the incidence of disease. This was quickly followed by new knowledge of anatomy, physiology and pathology. At the end of the first half of the 19th century a beginning had been made in the discovery of specific organisms in diseased tissues and by the end of the century the literature on Bacteriology and Parasitology (see BACTERIA AND DISEASE ; PARASITIC DISEASES) had become enormous.
Concurrently with the growth of medical knowledge there was an empirical movement of practical pre vention. Long before the days of Hippocrates men had sought to stem the tides of disease which threatened to overwhelm them. Even in Britain it was the ravages of pestilence in the Middle Ages—of leprosy from the 12th century, of the Black Death from the 14th, of sweating sickness in the 16th, and of cholera and smallpox subsequently—which compelled attention to the condi tions which seemed responsible for these scourges. The great monastic orders and some of the historical cities—Rome, Venice and London—provided comfort, refuge and sustenance for the victims, and in 1388 was passed the first Sanitary Act in England, directed to the removal of nuisances. In 1443 came the first plague order recommending quarantine and cleansing; in 1518 were made the first rough attempts at notification of epidemic disease and of isolation of the patient ; under Queen Elizabeth scavenging became more stringent ; and as time passed men began to see that environment was one of the principal factors in the origin and spread of disease.
At first the new applications of medicine were suggested by medical practitioners. Three centuries ago Harvey indicated for us the true experimental method ; he placed the blood in the forefront of physical life, and gave it a new chemical and physiological meaning, and by his demonstra tion of the circulation he provided a new conception of the method by which the blood carried its nourishment to all parts of the body. Fifty years later, Thomas Sydenham, another practitioner, living in a "generation of the strongest and most active intellects that England has produced," laid the basis of epidemiology by his ob servation of cases, his power of analysis and comparison, his deduction of laws of prevalence, and his suggestive hypothesis of "epidemic constitutions." Richard Mead, a successful English practitioner in the first half of the 18th century, left behind him published works on poisons, on the plague and the methods of its prevention, on smallpox, measles and scurvy. Bradley and Rogers deduced from their general practice some of the principles of epidemiology, Fother gill described "putrid sore throat," and Haberman chickenpox. Huxham, of Totnes, became an authority on the treatment of fevers, recommended vegetable dietary in cases of scurvy and defined Devonshire colic, which his medical neighbour, Sir George Baker, traced to lead in the vats and cider presses. Willan made a systematic study of the health conditions of London. Withering, of Shropshire, contributed to our knowledge of the incidence of scarlet fever, analysed water, was a climatologist and used digi talis. Edward Jenner, a practitioner in Gloucestershire, introduced vaccination. James Lind issued the first treatise on scurvy and the health of seamen. Thackrah, who practised in Leeds, explored industrial health problems and described dust diseases and brass f ounders' ague, and Michael Taylor of Penrith was the first to elucidate milk-borne epidemics. Indeed, the 18th and 19th cen turies furnish a remarkable record of clinical discoveries which prepared the ground for the study of causation and the influence of external environment in relation to communal disease.