Summary

Robert Koch’s 1876 monograph establishes that the bacterium *Bacillus anthracis* is the specific, necessary cause of anthrax, disproving spontaneous generation and demonstrating the first direct link between a microorganism and a mammalian disease. Koch isolates the bacillus from infected animals, grows it in pure culture using sterile blood serum, and injects it into healthy mice, which then develop anthrax and die. He further observes that the bacillus forms dormant spores that survive in soil and can later infect new hosts, explaining the disease’s recurrence in grazing animals. The work introduces key experimental methods—pure culture, animal inoculation, and microscopic documentation of the pathogen’s life cycle—that become foundational for germ theory. A reader takes away a clear, step-by-step proof that a specific microbe causes a specific infectious disease, along with the experimental protocols that define modern bacteriology.

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Key concepts

Bacillus anthracis — The rod-shaped bacterium identified by Koch as the etiological agent of anthrax, isolated from infected animal blood and tissues.
Spore formation — The process by which *B. anthracis* produces dormant, heat-resistant spores that persist in soil and initiate infection upon ingestion by herbivores.
Pure culture — Koch’s method of growing the bacterium in sterile blood serum or on solid media to obtain a single, uncontaminated strain for experimental inoculation.
Animal inoculation — The experimental technique of injecting pure bacterial cultures into healthy mice to reproduce the disease and fulfill Koch’s criteria for causation.
Koch’s postulates (implied) — The logical framework—though not yet formally stated—that the microbe must be present in all diseased organisms, isolated, grown in pure culture, and cause the same disease when introduced into a healthy host.
Spontaneous generation refutation — Koch’s demonstration that anthrax arises only from preexisting *B. anthracis* cells or spores, not from nonliving matter.