Yelp -- If you already have a background in medicine, much of the info in this book may seem "dumbed down" but it personally got me through severe dysentery, heat stroke, sinusitis, and helped me to administer minor first aid to several villagers (burns and cuts) and discuss good nutritional/hygienic practices with them.

I left my copy behind when my service ended, but found and printed out the first aid chapters online a number of years ago. I believe I got it from the Hesperian Foundation, which graciously distributes it for free.