Six pairs of sailors

About this video

In the 1700s, sailors on long voyages often got scurvy. It made them very tired and weak, with swollen gums and pain in their legs, and many died. We now know it comes from having too little vitamin C, which is in fresh fruit and vegetables, for a long time. Doctors then had many ideas about how to cure it, and no way to tell which idea was right.

On 20 May 1747, on the ship HMS Salisbury, the doctor James Lind took 12 sailors with scurvy. Their illness was as alike as he could find, they stayed in the same part of the ship and ate the same food. He put them in six pairs, and each pair got one extra treatment every day: cider, a few drops of a weak acid, vinegar, seawater, two oranges and a lemon, or a spicy paste. The pair who ate the oranges and lemon got better fastest: after about six days, when the fruit ran out, one of them was fit to work again. The cider pair came second. Because the food, the place and the time were the same for everyone, the extra treatment was the likely reason for the difference. That is a fair test of a treatment.

Lind's test had real limits. There were only two sailors on each treatment, Lind chose the pairs himself, and everyone knew who got what. He didn't fully understand his own result either: later he suggested a fruit juice boiled down to keep on long voyages, and the heat destroyed much of what made it work. Only in 1795, almost 50 years later, did the British Navy start giving lemon juice to its sailors on a large scale.

A clinical trial is a fair test of a treatment in people. Today's trials follow Lind's idea and fix his limits: they include many more people, chance rather than the doctor decides who goes in which group, and a control group gets the usual treatment or a look-alike with nothing in it. Then the groups are compared. This video explains clinical trials on Knaph, from the Health Level 1 lesson Lemons at Sea.

Transcript

1. 0:00In the 1700s, sailors on long voyages got scurvy. Swollen gums, aching legs, and many died. How could anyone find a cure that worked?
2. 0:10In 1747, on HMS Salisbury, James Lind took twelve sailors with scurvy. Same place, same food. Six pairs, and each pair got one extra treatment. Cider, a weak acid, vinegar, seawater, oranges and a lemon, or a spicy paste. The fruit pair got better fastest. Cider came second. Only the treatment was different, so it was the likely reason.
3. 0:34But the test had limits. Two sailors per treatment, Lind chose the pairs, and everyone knew. The Navy only gave sailors lemon juice on a large scale from 1795.
4. 0:48Today's clinical trials fix those limits. Many people, chance decides the groups, and a control group gets the usual treatment or a look-alike. Then the groups are compared.
5. 1:04Compare groups alike in every way but one.