A concise synthesis of the structure and changes in 66 years of American medical practice--by a respected investigator in social medicine. (Planned to cover 100 years, the work was cut short by the author's death.) Rosen, professor of the history of medicine, epidemiology, and public health at Yale, viewed medicine as a social function with a fundamentally economic aspect--not as a self-contained series of scientific developments. Today, this is hardly an unusual viewpoint (see, most recently, Paul Staff's The Social Transformation of American Medicine); but Rosen was one of those who pioneered the approach. He identifies the second half of the 19th century as the first period of meaningful change in medicine; before that, principles of practice were so stagnant that ""the assumptions and practices of George Washington's physicians would in most respects have been immediately understandable to the medical men who treated Julius Caesar."" From that time on, there was a fundamental change--from family-based, home-oriented care which could be rationalized in commonly understood terms, to a treatment system guided by concepts ""inaccessible to the ordinary patient,"" aided by a rapidly expanding technology, and conducted largely in impersonal institutions. Rosen divides the roots of this charge into two time periods. From 1875 to 1910, the major precipitating factor was competition, which involved educational reforms, banishment of non-physician practitioners, and the first influx of foreign-trained medical men (a harbinger of future uproars in the profession). The second period, from 1910 to 1940, was marked by the Flexner Report (which Rosen interprets as a consequence, not a cause), an explosion in medical knowledge (with an attendant increase in specialization), the securing of physician control, and stabilization of the medical market. Familiar material or not: seen through a master's eye.