boiling surgical instruments?

[Dan D'Silva]

And why did they recommend bleeding a man opposite to where he had received a wound and already was bleeding profusely?
Just because they did A right didn't mean they automatically also got B right.

I certainly wouldn't argue that. I rather assume that they did what seemed to make sense to them, even if it makes no sense at all in hindsight.

What I mean is that someone noticed that doing something seemed helpful, and that bit of knowledge got passed around. Sometimes it's still a good idea once we're able to understand how it worked, and sometimes it only "worked" through sheer luck because the treatment itself was meaningless.