So, what's the difference between Osteopathic and Chiropractic medicine?
Over the subsequent years, Still and the growing D.O. community integrated the Osteopathic principles and practices into their practice of medicine. That is, they would still use drugs or perform surgery if needed, but their general maxims were "Above all, do no harm." and "Keep it pure." In other words, D.O.'s were not defined by manipulation, rather, they were defined by their philosophy and manipulation/palpation happened to be a "really good tool" that was used. (In all honesty, D.O.'s didn't all agree that they wanted to do this; they were spurred on to do this by changes that were going on within the allopathic community, the Flexner Report on medical schools, etc.) D.C.'s, on the other hand, limited their practices strictly to manipulation, and did not teach "materia medicae" (essentially, medical therapeutics) in their schools at the time.
OK, back to the 1990's: Is there any difference between manipulation between a D.O. and a D.C.? Probably not. There are many different ways to mobilize joints and which technique is selected is more likely based upon the skill and comfort of the practitioner, not to mention the size/shape of the patient. I have chiropractic friends (who recently entered D.O. school incidentally) who would adjust me when I would need it using techniques very similar to mine.
How much manipulation training do D.O.'s receive? I can't quote the exact number of hours but they were a lot. In addition to our regular traditional medical school classes (anatomy, biochemistry, pharmacology, etc.), we would have at least one hour of Osteopathic Principles and Practices each day, for each semester that we were in classes. So generally, we spent longer times in school each day, in comparison to our M.D. colleagues.
What about holistic medicine? Do M.D.'s practice holistic medicine? As I noted, the concepts of structure and function being inter-related, etc. have all been pretty much accepted by the medical community nowadays, but whether or not most M.D.'s actually think about this is another matter. Philosophically, Osteopathy can be considered more closely aligned historically with Chinese medicine, which took a holistic approach. Allopaths (M.D.'s) philosophy stems way back to ancient Egypt where they used to have individual gods for different things. Body parts were sort of compartmentalized - there may have been a god to care for extremities, another for chest, etc.. This type of thinking does not lend itself as well to a holistic approach. The result today: the majority of D.O.'s practice primary care medicine and the majority of M.D.'s specialize.