Clinical arithmetic

An Enlightenment legacy still needs defending—against more subtle adversaries

”On the 20th of May 1747, I took twelve patients in the scurvy, on board the Salisbury at sea. Their cases were as similar as I could have them. They all in general had putrid gums, the spots and lassitude, with weakness of their knees.” So begins James Lind's brief 1753 account of how he identified “the surest preservative, the most efficacious remedy” for a disease that in his time could kill sailors in their hundreds every year. In a comparison of six treatments—cider, elixir vitriol, vinegar, sea water, a laxative, and citrus fruit—the last produced “the most sudden and good effects,” despite a shortage of oranges and lemons that limited treatment to only six days.1 Thus a naval surgeon and a dozen seamen in six groups of two entered medical history, with both a cure for scurvy and an enduringly powerful method, the controlled clinical trial.