How Did They Run Ventilation Systems in the Old Days?

James Lileks wonders:

I had to buy air filters for the house this weekend. There's a central fan that moves the air around. Why, I have no idea. When the house was built 90 years ago, people had to move the air around the old-fashioned way, perhaps by filling balloons upstairs and emptying them in the basement. Or they hired neighborhood kids to be "zephyr boys," running around the house flapping leather wings.

I thought they used draft animals back then.

Disclaimer: The same pun can be found in Tatja Grimm's World by Vernor Vinge.