An injured Afghan National Army soldier is helped from a medevac helicopter, which transports casualties of war as well as sick and injured local residents.

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When human lives are in your hands, as is the case with physicians, the question of what is right and what is wrong becomes quite literally a matter of life and death. And the right choice isn't always easy to see.

This is why we have, for example, the American Medical Association's (AMA) Code of Medical Ethics, a body of work that defines honorable behavior for a health care professional.

The 1847 code of ethics from the fledgling AMA was a much shorter document than today's. Doctors were exhorted to unmask quacks and refrain from advertising and concocting their own patent medicines. Proper patient behavior was described as well -- stick to one doctor only, so he knows your whole history; tell your doctor all, including the embarrassing things (even you, ladies); and, our personal favorite, don't tell your doctor long, tedious tales.

These issues are, of course, still a concern (although the part about not irritating your doctor with your poor storytelling skills is no longer spelled out). Physicians continue to battle fraudulent medical practices -- for example, chelation therapy for autism, an expensive treatment that is only medically approved for heavy metal poisoning. And it's just as important that your treating physician have access to your entire medical history, only now we're hoping to accomplish the same thing through different means -- electronic health records, perhaps.

Today's code of ethics covers everything from reporting colleagues with substance abuse problems to accepting gifts, using placebos and do-not-resuscitate orders. Despite the many, many subheadings, this document and 1847's original version attempt to answer the same question: What is a doctor's responsibility to his or her patients?

The question is complicated when it comes to a military doctor. It may seem only like an exercise in philosophy until you take it to where it matters: the battlefield. If it comes down to a conflict between a soldier's duty and a doctor's ethics, who wins?