Case Three: Yersinia pestis

The discovery of the plague bacterium, yersinia pestis, is deeply intertwined with the history of the plague as a tropical disease, explored in the center case. The bacterium was isolated in 1894 in Hong Kong by Dr. Alexander Yersin who worked for the French Pasteur Institute (it was also isolated in the same year by Kitasato Shibasaburō). The discovery of the entire “unholy trinity” of plague – bacterium, flea, rat – would follow in the coming decades. These findings forever changed the visualization of plague. Although the plague would continue to be imagined as a tragedy of epic proportions, it could also be visualized as a microscopic murderer, infecting and killing through bacteria undetectable to the human eye.

The science of bacteriology and the imaging technologies of the early twentieth century made it possible to create pictures of the plague bacteria. The plague could now be seen as tiny infectious dots made visible by the microscope. Klein’s “Studies in the bacteriology & etiology of oriental plague” reinforced the plague as a tropical disease infecting the “orient.” The book includes images of plague bacterium in the human, rat and guinea pig.

Yersin et la peste: ouvrage publié pour le cinquantenaire de la découverte du microbe de la peste. Bernard, N. Lausanne: F. Rouge, 1944. W7.YER.HAU 1

This 1944 French text about the discovery of the plague bacterium by Alexander Yersin includes several photographs of the pioneering scientist and his discovery. The image at the top of this page is of his laboratory in Hong Kong, complete with thatch roof. Also shown here is a copy of the letter where Yersin reported his discovery, a portrait of him dressed as a colonial explorer, and a group photograph of the Pasteur Institute researchers.

Today you can easily buy a plush yersinia pestis microbe, multiplied to a million times its actual size, on the internet. No longer the terrifying killer of yesteryear, you can feel free to cuddle with this once murderous microbe.