Читать книгу Science: A History in 100 Experiments - John Gribbin - Страница 18

No. 13

VITAMIN AT SEA

There is a particular kind of experiment that is important in everyday life, although it is not usually called an ‘experiment’, perhaps for fear of worrying the people taking part. This is the ‘medical trial’ – a kind of controlled experiment. One of the best examples of a medical trial is also one of the earliest, dating from the 1740s, when James Lind, a surgeon in the Royal Navy, carried out experiments to find a cure for scurvy. The story of scurvy also shows the value of careful experiments and observations, even when it takes a long time for these observations to be explained.

Scurvy is an illness that starts out with a general feeling of being under the weather and lethargy, then develops with spots on the skin, softening and bleeding of the gums, loss of teeth, open wounds on the skin, and eventually death. We now know that it is caused by a lack of vitamin C, but in the eighteenth century nobody knew anything about vitamins. What they did know was that scurvy was prevalent among sailors and soldiers on a restricted diet of dried meats and grains. The problem was highlighted by the fate of the first British circumnavigation of the globe, by a fleet led by Sir George Anson between 1740 and 1744. Out of an initial complement of about 2,000 men, more than half died from scurvy on the voyage. For a growing naval power such as Britain, finding a treatment or preventative for scurvy was a pressing problem.

© St. Mary’s Hospital Medical School/Science Photo Library

The mouth of a person suffering from scurvy, showing swollen and bleeding gums.

Lind was not the first person to suggest that citrus fruits might be used to treat scurvy, but he was the first person to carry out a scientific experiment to test the idea. His ideas about the cause of scurvy were completely wrong – he thought it was caused by a ‘putrefaction’ of the body, which he hoped to treat with acids. On a voyage in 1747, he tested this idea by adding different acids as supplements to the diet of different groups of men afflicted with scurvy. All the sailors ate the same foods, but every day one group had a quart of cider each, one group had 25 drops of elixir of vitriol (sulphuric acid) added to their diet, one group took six spoonfuls of vinegar each, one group had to drink half a pint of seawater, the members of another group each ate two oranges and one lemon a day, and the last group drank barley water and ate a spicy paste. The seawater drinkers were a ‘control’, because they were not given any medicine. Hence the term ‘controlled experiment’. By the time the experiment ended (because the ship had run out of fruit) the health of the sailors given oranges and lemons had improved dramatically; among the other groups, only the cider drinkers showed a slight improvement.

© Science Photo Library

James Lind (1716–1794).

The Royal Navy took note of the discovery, and some captains began to implement a policy of providing ships with a syrup made from oranges, and also with sauerkraut, which had also proved an effective antiscorbutic (from the Latin term for scurvy, scorbutus). Lind left the service soon after this voyage, and although he wrote a book, A Treatise of the Scurvy, which was published in 1753, it was largely ignored. But a second ‘experiment’ was carried out by James Cook on his first circumnavigation of the globe, starting in 1768. His ship carried three tons of sauerkraut. This tasted vile, but Cook persuaded his crew to eat it by a ‘method I never once knew to fail with seamen’. He had the food served at first only to officers, who ate it with the appearance of delight. The men soon petitioned for it to be added to their rations, and the result was that there were hardly any incidences of scurvy.

Although shore-based doctors continued to ignore the evidence, experience had shown the Navy what worked, even if they did not know why it worked. In 1794, lemon juice was issued to sailors on board the Suffolk on a 23-week voyage to India during which nobody died from scurvy. A year later, lemon juice began to be issued to every ship. The juice proved quite palatable, since it was drunk mixed with the sailors’ ‘grog’, a ration of rum diluted with water. This was later replaced by lime juice, which proved even more effective, and, by the middle of the nineteenth century, American sailors had begun referring to their Royal Navy counterparts as ‘lime-juicers’ – later shortened to ‘limeys’ and applied to anyone from Britain.

It was not until the early 1930s that the active ingredient was identified and named ascorbic acid, or vitamin C. Most animals can make their own vitamin C, but monkeys and apes (including humans), guinea pigs and bats are among the few who cannot do so and have to get vitamin C through their diet.