At Göttingen, Koch apparently had little encouragement to study
bacteria because, as he later observed, "bacteriology did not exist at that
time." ⁴ But in Wollstein, Koch became intensely interested in this rela-
tively young field of study, and he assembled his own laboratory. On one
birthday, his wife presented him with a good quality microscope. Koch's
makeshift laboratory was located in a small room adjacent to his consul-
tation office. He had an incubator, a sink, a work bench, and, later on, a
small dark room. Koch apparently trapped in his barn and garden many of
the animals that he used in his experiments. Having no financial support
for such work, Koch himself was obliged to bear the expenses of his
research. ⁵ In 1873, Koch began to investigate anthrax, a disease that
affected both humans and animals and that was especially rampant in the
sheep herds of the area around Wollstein.

By the time Koch began his studies of anthrax, considerable evidence
had been accumulated in support of the possibility that microorganisms were
significant in the etiology of disease.

From the late seventeenth century, such persons as Anton van
Leeuwenhoek had investigated and classified microorganisms. Among the
first clearly to associate them with specific disease processes, however, was
Agostino Bassi who, during 1835 and 1836, published investigations showing
that muscardine, a disease fatal to silkworms, was due to a minute fungus. ⁶
In 1839, Johann Lucas Schönlein discovered that favus, a skin disease, was
due to another fungus. ⁷ In the next year, Jacob Henle, who was later one
of Koch's teachers in Göttingen, speculated that microorganisms may be
causally responsible for various diseases. ⁸ In 1847 Ignaz Semmelweis
demonstrated the usefulness of chlorine disinfection in preventing childbed
fever. ⁹ Semmelweis's own interpretation of his results was generally
rejected, and neither Semmelweis nor any of his contemporaries seem to
have immediately recognized the connection between his work and the
possibility of parasitic infection; somewhat later, however, the connection
became clear.

Beginning in 1857, Pasteur published a series of investigations of
fermentation, and reached the conclusion, as others had before him, that
alcoholic fermentation was always due to the growth of living yeast
organisms. ¹⁰ This work had important practical applications in the vinegar,
wine, and beer industries. It was also theoretically significant because
certain disease processes such as septicemia involved decomposition of
animal tissues, and such decomposition was generally associated with
fermentation. In a series of papers that overlapped his work on fermen-
tation, Pasteur also argued very persuasively against the long-standing
belief in spontaneous generation. ¹¹

Through the third quarter of the nineteenth century, investigations of
various specific diseases clearly supported the possibility that micro-
organisms could cause disease. (1) By 1850 Casimir Davaine and Franz
Alloys Antoin Pollender had identified small rods in the blood of animals
that died of anthrax. Experiments established that blood containing the
rods was infectious. In 1857 Friedrich August Brauell demonstrated that
While the blood of a diseased pregnant female animal, which contained the
rods, was infectious, the blood of its fetus, which resembled the blood of
its mother in every respect except that it did not contain the rods, was not
infectious. ¹² Over the next decade, Davaine published a series of important
papers in which he argued that the rods caused anthrax. ¹³ (2) In 1863 and
in 1865, Karl Mayrhofer reported finding certain microorganisms, which he
called vibrions, in tissues and secretions of women who suffered epidemic
puerperal fever. ¹⁴ Mayrhofer's work, which seems clearly to have been
based on Semmelweis's discoveries, also drew on Bassi's investigations of

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