As if to instantly affirm the principle that progress cannot continue on a simple and direct path, the Romans came after the Greeks and took medicine on a new and far less rigorous path. Seeing the Greeks and their dependence on physicians as effeminate, Romans insisted that exercise and diet, with a few traditional herbal remedies utilized only due to past practice and not an empirical evidence, was all that was needed to maintain health. Despite other advances in hygiene and the amazing civil works projects the Romans were able to undertake and complete, historians have generally agreed that their knowledge and practice of medicine was inferior to that of the Greeks, possibly vastly so. Though health was indeed promoted by many of the Roman's activities and endeavors, medicine was actually one of the areas in which the least progress was made, and that had the least positive and direct benefit on the health of the large population of the Roman empire.
Following the fall of the Roman Empire, subsistence farming again became the way of life across Europe, and it was not until the eleventh century CE that farming surpluses again allowed for renewed attention towards the body and its ailments. Rediscoveries of -- and renewed appreciations for -- Greek and Roman medical texts allowed for medical investigation to pick up not exactly where it began, but with a certain level of continuity. Of course, this "continuity" was only achieved after nearly a thousand years in which almost no progress was made in the science of medicine, due to a combination of religious taboo and limited resources. The easing of both issues allowed medicine to again be seen as a worthy...
The practice if inoculation, for instance, was adhered to by many without being fully understood; it was seen that giving a minor form of a disease to individuals would give them a lifelong immunity to the disease, but the mechanism for this was not understood nor were there really empirical trials to prove this at first, The practice was brought to Europe, in fact, after being witnessed among the Turks -- it had nothing to do with the progress of Western scientific medicine. The non-linear nature of this discovery is accented still further when it is noted that it was not until the twentieth century -- more than three hundred years after inoculations began being practiced in England -- that the identification of antibodies and surface marker proteins that are part of the current explanation for how immunities develop were identified, and the process made clear in a true cause-and-effect manner. Medicine, that is, is still filling in gaps in its knowledge that have existed for centuries, and it will likely continue to do so for centuries more.
Medicine, like all human knowledge, is a collective endeavor. This, coupled with major changes in the overall trajectory of human civilization, has meant that medicine's progress has been in several direction, sometimes backwards, at different times. Though there has certainly been progress in medicine overall, it has not been in a straight line -- nor would many current advancements have occurred if it was.
