My thoughts were set to spinning while Amy and I were watching HBO's "Something the Lord Made" and she pointed out that Doctor Blalock and his assistant, Vivien Thomas, wiped their hands on a cloth towel when washing up after surgery. I thought, Nowadays, (although some restrooms still hold only cloth towels--albeit the kind that rotates) the average person probably knows that this is an example of poor hygienic practice; and most of us who know probably take it for granted that we know! And yet, as late as the 1940s, even surgeons did not weren't aware of this "simple" fact; the discovery was not yet well-know or even made yet.

What other discoveries--not necessarily inventions, but progressions of knowledge--that, if we were to go back in time, we would sorely miss, but which we take for granted now, can you name?