In the 1850s, Pasteur was asked to study why products of fermentation, such as wine and beer, sometimes sour during production. He soon demonstrated that a specific microscopic organism causes each kind of fermentation, and that when other microorganisms get into the liquid, they can cause souring. He also showed that "germs" cause milk to sour and cause infectious diseases. Pasteur found that he could kill many microorganisms in wine by heating and then rapidly cooling the wine--a process now called Pasteurization. While developing methods for culturing microorganisms in special liquid broths, Pasteur discovered that some microorganisms require air--specifically, oxygen--while others are active only in the absence of oxygen. He called these, respectively, aerobic and anaerobic organisms. In 1877 Pasteur began to study Anthrax, a disease mainly of cattle and sheep. He developed a vaccine using a weakened strain of the Anthrax bacterium. In 1885 he developed the first vaccination against Rabies in humans.