Today in 1870, US Patent 101966 A was issued, an invention of Felix Manz, for his “Improvement in Beer-Faucets.” There’s no Abstract, although in the description it includes this summary:

The nature of my invention consists in constructing a beer or ale-cock in such a manner that, as the beer or ale is drawn from the’ barrel, the faucet by means of a plunger contained init, will force the beer or ale through the valve, thereby causing the old, as well as new beer, to produce a rich creamy surface.