In 1890, Koch returned to his work on tuberculosis. He sought to arrest the disease by means of a preparation, which he called tuberculin, made from cultures of tubercle bacilli. He made two preparations of this kind called the old and the new tuberculin respectively, and his first communication on the old tuberculin aroused considerable controversy. Unfortunately, the healing power that Koch claimed for this preparation was greatly exaggerated and, because hopes raised by it were not fulfilled, opinion went against it and against Koch. The new tuberculin was announced by Koch in 1896 and the curative value of this also was disappointing; but it led, nevertheless, to the discovery of substances of diagnostic value. While this work on tuberculin was going on, his colleagues at the Institute for Infectious Diseases, von Behring, Ehrlich and Kitasato, carried out and published their epoch-making work on the immunology of diphtheria.
- Nobel Lectures, Physiology or Medicine 1901-1921, Elsevier Publishing Company, Amsterdam, 1967