Medicine in Britain c1250–present & the British sector of the Western Front

I largely agree with the statement¹. Before 1861 most people, including doctors, explained disease through miasma, the four humours or spontaneous generation; by 1900 doctors accepted that particular microbes caused particular diseases. Pasteur's germ theory was the turning point in that change, because it was the first idea to be supported by repeatable experiments. However, it did not change ideas on its own: it depended on improved technology, it was only fully convincing once Robert Koch linked specific bacteria to specific diseases, and in Britain the old ideas lasted for many years after 1861.

The strongest case for the statement is that germ theory replaced spontaneous generation, the belief that microbes were produced by decaying matter. While investigating why wine and beer went sour for French industry, Pasteur showed that microbes in the air caused decay. In his swan-neck flask experiments², sterilised liquid stayed fresh when its curved neck trapped airborne microbes, but went bad when the neck was broken. This proved that microbes came from outside and caused the decay, rather than being produced by it, and in 1861 he published his germ theory. This was a fundamental change because, for the first time, the cause of decay – and by extension disease – was something that could be seen, tested and attacked³. Without this idea, later breakthroughs such as Lister's carbolic acid antiseptic (1867) would not have had a scientific basis.

However, Pasteur's 1861 theory was about decay, not about which germ caused which illness, so the work of Robert Koch was just as important⁴ in changing ideas about disease. Koch identified the bacterium that caused anthrax in 1876, then tuberculosis in 1882 and cholera in 1883. Crucially, he developed methods that let other scientists check his findings: staining bacteria with dyes so they showed up under the microscope, photographing them, and growing pure cultures on a solid medium such as agar. Because Koch proved that a specific microbe caused a specific disease, doctors could no longer dismiss germs as a vague theory. This suggests that the change in ideas came from germ theory as developed by both men, not from Pasteur alone.

Science and technology was an essential factor underpinning both scientists. Microbes had been seen by van Leeuwenhoek in the 1670s, but early microscopes blurred images too much to study them. Improvements in the 1830s, especially the achromatic lens designed by Joseph Jackson Lister⁵, gave far clearer magnification, and by the later nineteenth century microscopes were good enough for Koch to photograph individual bacteria. Rivalry and government support also mattered: after the Franco-Prussian War (1870–71) the French and German governments funded Pasteur's and Koch's teams, and the competition between them sped up the identification of microbes and the development of vaccines in the 1880s. Germ theory therefore needed technology and funding to turn an idea into accepted knowledge.

Finally, the limits of germ theory's impact in Britain weaken the statement. Even after 1861, many British doctors and officials still believed in miasma; the physician Henry Bastian⁶, for example, publicly argued for spontaneous generation into the 1870s. Ideas about cholera had already started to shift before germ theory, when John Snow mapped deaths around the Broad Street pump in 1854 and showed that the disease spread through contaminated water – although he could not explain what in the water caused it, and the authorities were slow to accept his findings. Ideas changed gradually, and full acceptance in Britain only came in the 1880s and 1890s, after Koch's discoveries.

Overall, I agree with the statement to a large extent. The best way to judge the 'main' reason is to ask which factor all the others depended on⁷. Microscopes, government funding and Koch's methods all made germ theory stronger, but they were valuable because they tested or built on Pasteur's central idea that microbes cause decay and disease. Without germ theory, better microscopes would simply have shown more microbes without explaining them. However, germ theory alone did not change most people's ideas: it needed Koch's proof, technology and time, which is why the change was gradual rather than sudden.

Source A is very useful for an enquiry into the problems of moving wounded soldiers¹ because it describes several of those problems from first-hand experience. It shows that the narrow, zig-zag trenches slowed stretcher-bearers down, so that it took over an hour to carry one man half a mile, and that continuous shellfire made the work dangerous. It also reveals that wounded men in No Man's Land could not be reached until dark. This fits what I know about the Battle of the Somme: on 1 July 1916 alone the British suffered around 57,000 casualties², far more than the stretcher-bearers and Regimental Aid Posts could handle quickly, and many men waited hours or days for rescue. The provenance adds to its usefulness. It was written by a stretcher-bearer – the person who did this job – during the battle, and as a private letter to his family he had no reason to exaggerate³; in fact he says he does not want to worry them. However, it is only one man's experience over three days, and letters home were read by army censors⁴, so he may have left out the worst details.

Source B is useful because it shows a different problem: the terrain. The mud is knee-deep and the ground is full of shell holes, so six men are needed for one stretcher instead of the usual four⁵, and there are no roads for motor ambulances to use. This matches my knowledge of the Third Battle of Ypres (Passchendaele) in 1917, when heavy rain and constant shelling destroyed the drainage of the low-lying land and turned it into a swamp, so that carrying a man to the aid post could take hours. As an official photograph it is useful because it records a real scene at the time rather than someone's later memory. However, official photographs were taken by army-approved photographers and passed by censors, so this one may have been chosen or posed to show the bravery of the stretcher-bearers⁶. It also shows a quiet moment with no shellfire, so it does not show the danger described in Source A.

Overall, both sources are useful, and they are most useful together: Source A shows the problems of trenches, shellfire and the scale of casualties, while Source B shows how the ground itself made evacuation slow and exhausting.