Botulinum toxin
In 1895 (seventy-five years later), Émile van Ermengem, professor of bacteriology and a student of Robert Koch, correctly described "Clostridium botulinum" as the bacterial source of the toxin. Thirty-four attendees at a funeral were poisoned by eating partially salted ham, an extract of which was found to cause botulism-like paralysis in laboratory animals. Van Ermengem isolated and grew the bacterium, and described its toxin, which was later purified by P Tessmer Snipe and Hermann Sommer.
Tuberculin
Tuberculin was discovered by German scientist and physician Robert Koch in 1890. The original tuberculin discovered by Koch was a glycerine extract of the tubercle bacilli and was developed as a remedy for tuberculosis, but reductions in deaths did not meet those expected of the treatment. British efforts to set up 'dispensaries' for the examination, diagnosis and treatment of the poor achieved better results as the Edinburgh System structure encompassed treatment of the homes and entire contacts of the TB sufferers. The example of Dr Hilda Clark's dispensary at Street, Somerset was especially marked for its efficacious treatment of the less severe cases. Clemens von Pirquet, an Austrian physician, discovered that patients who had previously received injections of horse serum or smallpox vaccine had quicker, more severe reactions to a second injection, and he coined the word "allergy" to describe this hypersensitivity reaction. Soon thereafter von Pirquet discovered the same type of reaction took place in those infected with tuberculosis, and he thus found the utility of what would become the tuberculin skin test. Individuals with active tuberculosis were usually tuberculin positive, but many of those with disseminated and rapidly progressive of disease were negative. This led to the widespread but erroneous belief that tuberculin reactivity is an indicator of immunity to tuberculosis.