I come from a family of biology geeks and animal lovers, and if I'd been a bit more, um, focused in college, I might have gone to veterinary school. I had to content myself with grad school instead, but I've always been interested in medicine, both human and animal. I've also always loved fantasy, so when I decided to get off my butt and actually write a novel, it's not surprising a certain amount of biology and medicine came into it.
In my first novel Umbral Heretic, which is now being polished for submission, my protagonist is a rather hapless guy who is addicted to a magic that's forbidden for a very good reason--it uses physical and psychic pain to warp the life force of its victims. Umbral magic is connected to life magic, which is used by healers to, well, heal.
My secondary protagonist is a healer. Healers are common in fantasy novels, so I had to spend some time thinking of how I wanted to make this character stand out from the pack by having my healing magic be a bit more than simple hand waving.
This necessitated some research. The thing that really hit me is how dependent modern medicine is on technology. It's really common to run across fantasy settings where the healer gives a patient some miraculous potion or herbal concoction that kills pain, banishes infection or puts the person to sleep as effectively as modern drugs do. This seems just a tad unrealistic to me.
Another serious problem faced by early physicians was a lack of knowledge of the inner workings of the body. Until microscopes came along in the 16th century, people didn't know the body was constructed of cells, and the microbialtheory of disease wasn't widely accepted until the 19th century. Without x-ray machines and other, more advanced imaging tools, they couldn't look inside the living body. Physiologists didn't even know how blood circulated until the mid sixteenth century. Mummery and quackery abounded, and even the most meticulous and advanced physicians of their times (people like Hippocrates, Hua Tuo and Galen) based their healing on hypotheses they had little means of testing.
So I had to spend some time researching when and how various things, from microscopes (late 1500s) to hypodermicneedles (early 1800s) were invented in our world. I also had to learn when varioussurgical techniques (from antiquity to 1800s) were first performed successfully and when various concepts like hygiene (antiquity) came into existence.
These numbers created some problems for my tale, since they were so all over the place. I really didn't want to present my healing as being modern, but I didn't want it to be all bloodletting and purges either. The setting is a society that was roughly in line with the mid to late renaissance in terms of social organization, technology level and overall "feel." But certain plot elements needed for there to be medicine that was a bit more sophisticated than it was in the "real" 17th century, and I wanted some elements of society at least to be undergoing a period of rapid change and enlightenment.
And this is in fact what drives some of the conflict in my novel, the overwhelming majority of which does not take place in a medical setting.
So I've tried to interweave my "physical" magic system into the existing world. I've discovered that it requires some care. While sophisticated healing is common in fantasy, it often involves miracles without any real explanation of the healers' knowledge of the workings of the body. While I don't provide a lot of details about the process of healing in my novel, I do have some scenes taking place in an infirmary setting, and the narrative spends some time in my healer character's point of view, so I can't gloss the details over completely.
And I've discovered (re comments from my beta readers) that as soon as a writer starts shuffling history's deck a bit, he or she invokes suspension of disbelief issues. Magic or no magic, there's no reason discoveries and inventions have to follow the same sequence in every culture (in fact they didn't in the Earth's various civilizations and cultures either). But whether or not this is true, some readers will still wonder why a healer in a pre-industrial setting is boiling her surgical instruments if aseptic technique didn't become established until the 19th century in our world. There's the old adage that it's relatively easy to get fantasy readers to suspend disbelief for the large things, like miraculous healing, but not smaller things, like magic that allows the development of microbial theory before steam engines make an appearance.
The comments from my readers have been invaluable here, as they pointed out some of the areas that need to be shown or justified a bit more carefully, and they provided me with some ideas of how to subtly (without info dumps) get across to readers that my setting is not your "default" socially, politically and culturally stagnant quasi-medieval fantasy world. In the end, there is probably no approach to world building that will please every reader, but I hope that my approach is novel enough to be interesting and plausible enough to be believable.
A collection of ancient surgical instruments found at Pompeii.
A 13th century medical illustration showing the major blood vessels. They did not differentiate between veins and arteries at this time, nor did they understand the mechanism of blood circulation.