Koch, Magic Bullets and Germ Theory in Britain

Pasteur had shown that germs cause disease. Robert Koch then found how to identify the exact germ behind each one, and these discoveries slowly reshaped British medicine.

Koch's method

• Robert Koch, a German doctor, worked out how to pin down the one microbe responsible for a particular disease.
• He stained bacteria with dyes so they stood out clearly under the microscope.
• He grew pure colonies of a single microbe on agar jelly in dishes, kept apart from all others.
• His four rules, known as Koch's postulates, set out how to prove that a specific germ causes a specific disease.

Koch's discoveries

Using these methods, Koch identified the exact bacteria behind three major diseases.

• Anthrax in 1876, the first disease firmly tied to one particular microbe.
• Tuberculosis (TB) in 1882, one of the biggest killers of the age.
• Cholera in 1883, which he traced to dirty water during an outbreak in Egypt.

Germ theory reaches Britain

• British doctors were slow to accept germ theory, and some held on to miasma until the 1890s.
• William Roberts and William Cheyne promoted it, with Cheyne translating Koch's work into English and using it in antiseptic surgery.
• Pasteur meanwhile made vaccines against anthrax in 1881 and rabies in 1885, showing germ theory could prevent disease as well as explain it.
• These ideas backed up public health reform, such as the 1875 Public Health Act.

Ehrlich and the first magic bullet

• Paul Ehrlich looked for a chemical that would kill one particular germ inside the body without harming the patient, which he called a magic bullet.
• His team tested hundreds of arsenic compounds and in 1910 found Salvarsan 606, which cured syphilis, a disease caused by the bacterium Treponema pallidum.
• It was the first chemical designed to target a single disease, and it pointed the way to modern drugs.