LOUIS PASTEUR The microbiologist signed and mailed this handwritten letter to politely decline an invitation Third person Autograph Letter Signed: "Mr. Pasteur". Signed "L. Pasteur" at conclusion. One page. 4½x3½ gray card. With original stamped envelope addressed by Pasteur. Postmarked Paris, France, May 22, 1886. In French (translated) to the Secretariat General of the Crédit Foncier. In full: "Mr. Pasteur regrets being unable to receive the kind invitation of the Managing Directors of the Crédit Foncier on May 29, 1886. L. Pasteur." Louis Pasteur (1822-1895) was a chemist and biologist who is considered one of a handful of the most important pioneers of microbiology. His body of work directly led to the development of vaccinations to protect humans from deadly diseases, the invalidation of the spontaneous generation theory of life, and the invention of pasteurization. Pasteurization is the process of heating dairy products to eliminate microbial organisms that can spread disease. Germ theory was already rapidly growing support, but Pasteur conducted controlled experiments from 1860-1864 that investigated germs, disease, and potential causality. These experiments put to rest any further serious opposition to the theory. While Pasteur's influence on microbiology and chemistry stretch far into the sciences, his notoriety today is primarily due to the namesake process of pasteurization used on virtually all dairy products sold in stores. Two small pinholes at blank top portion of letter and envelope. Otherwise, fine condition.