That one annoyed me, as I assumed that it was true when I read it in Ringworld (or whatever it was) and had it debunked a few years later. Not as badly as when I found out that leprosy is far more treatable than was stated in Donaldson's books about Thomas Covenant. I wouldn't be surprised if the described leprosy treatment had been true a few decades earlier, but I never got the impression that those books were set so early.