In the days surrounding Christmas 1874 Edward Klein was busy examining the stools of typhoid patients. Klein was working alongside John Burdon Sanderson—they were both subordinates of John Simon—in a special branch of the Medical Department colloquially known as “auxiliary scientific investigations.” On December 14 Klein received fresh stools of a patient who had been laboring for three weeks under the delirious fever spell of typhoid. On December 26, Boxing Day, he received more fresh stools from a second typhoid patient. They were “ochre-coloured, thin, composed of a clear fluid in which were suspended pale yellowish small and larger flakes and lumps,” Klein observed, “the well-known” characteristics of typhoid excreta. Klein macerated the fresh stools, mixed them with water, and bottled the concoction. With the aid of a microscope, he found what he was after: colonies of isolated, spherical micrococci “of a very characteristic appearance” (figure 4.1, marked “M”). When incubated for 24 hours at 39 degrees Celsius, they grew in number. In ten days, they were still growing “to an enormous extent.”

Klein had been at this for over a year, ever since the Marylebone Milk Crisis in the fall of 1873. He was probably the most dogged typhoid researcher in all of Europe, experimenting in his London laboratory on typhoid nearly every year until his death in 1910. It had been known from the late 1830s that typhoid produced pathological lesions in the small intestine. But not enough attention had been paid, Klein believed, to the “minute anatomy” of the disease. To what was only slowly coming to be called “bacteriology.” Armed with over a decade’s worth of “clinical observation” and “etiological data,” in other words, epidemiological evidence, Klein believed as did his department colleagues that “the contagion of enteric fever is a living organism.” It was an echo of Budd’s widely cited claim from his 1873 study Typhoid Fever and a germ theory in line with other Darwin-inspired doctors like Burdon-Sanderson and James Russell. If the poison, or germ, was to be found anywhere, Klein presumed, it would be in excreta and in and around the lesions in the small intestine. From September 1873 Klein