#187 1747 · James Lind, Royal Navy (HMS Salisbury) · Medicine / naval health
A ship's surgeon couldn't tell which of six competing scurvy cures worked, so he gave every pair of patients a different one at once
the problem
A killer with multiple competing folk remedies, none tested against the others, was bleeding a workforce for centuries
background
Scurvy killed more British sailors on long voyages than combat, storms and every other cause combined, and had done so for centuries by the time James Lind served as a naval surgeon aboard HMS Salisbury in 1747. Medical authorities disagreed on the cause and cure, and citrus fruit was just one of several remedies with anecdotal backers — cider, seawater, vinegar, diluted sulfuric acid and various tonics all had their own defenders, and no one had ever tested them against each other under matched conditions.
The standard practice was to pick a theory of the disease and treat accordingly, with no controlled comparison possible on land or at sea; a ship's surgeon simply had no way to isolate which of several confounded variables — diet, climate, treatment, individual constitution — was doing the work, so competing remedies persisted indefinitely on reputation rather than evidence.
what everyone would do
Pick a theory of the disease based on prevailing medical opinion and treat the whole crew accordingly, or try remedies one after another on the same patients over time. Both approaches confound the treatment with individual variation, changing conditions, and the passage of time, so any apparent improvement could always be explained away by something other than the remedy — producing more anecdote indistinguishable from the anecdotes already in circulation.
what they saw
Lind saw that answering which remedy actually worked didn't require a better theory of scurvy, it required a design that isolated treatment as the only thing differing between comparable patients tested at the same moment. Matching sailors on symptom severity, holding their housing and diet identical, and giving different pairs different remedies simultaneously meant any consistent difference in outcome could only be attributed to the treatment itself.
the move
Lind selected twelve sailors with comparably severe scurvy, matched them into six pairs, and gave each pair one of six remedies then in use — cider, elixir of vitriol, vinegar, seawater, a garlic-and-mustard paste, or two oranges and a lemon daily — while holding their housing and base diet identical, isolating the treatment as close to the only varying factor.
why it works
Because the twelve sailors were matched on severity and kept under identical housing and base diet, the only systematic difference between the six pairs was which remedy each received — removing the confounds (diet, environment, individual constitution) that had let competing remedies coexist on reputation for centuries. That design meant the citrus pair's rapid, unambiguous recovery against four pairs showing no improvement at all couldn't be dismissed as coincidence or explained by anything except the treatment, producing a result strong and clean enough to trust from a sample of just twelve men — something no amount of scattered anecdotal experience across a fleet could have delivered.
the payoff
Within six days the citrus pair had one sailor fit for duty and the other markedly improved; the cider pair improved slightly; none of the other four pairs improved at all — a clear, reproducible result from a trial of just twelve men.
where it breaks
The design only produces a trustworthy result if the treatment effect is genuinely large relative to individual variation; a small trial like this one has very limited power to detect a subtle or inconsistent benefit, and could just as easily miss a real effect or produce a false positive by chance. It also depends on successfully holding every other variable equal across groups — any residual difference in housing, exposure, or starting condition between pairs would undermine the causal claim. And even a clean, correct result doesn't guarantee it gets acted on: Lind's own later treatise buried the citrus finding among competing theories rather than stating it plainly, and the Royal Navy didn't mandate lemon juice rations until nearly fifty years later, after independent confirmation — proof that producing valid evidence and getting an institution to act on it are two separate problems.
what came after
Lind's design is now taught as one of history's first controlled clinical trials, but his own 1753 treatise buried the citrus result among other theories and the Royal Navy did not mandate lemon juice rations until 1795, after Rear Admiral Alan Gardner ran a scurvy-free voyage to India on HMS Suffolk — nearly fifty years after the trial had already answered the question.
references
- [1]Putrid gums and 'Dead Men's Cloaths': James Lind aboard the SalisburyJournal of the Royal Society of Medicine, 2003ncbi.nlm.nih.gov
- [2]James LindWikipedia, 2026en.wikipedia.org
- [3]Lind Discovers a Cure for ScurvyEBSCO Research Starters, 2023ebsco.com