The Disappearing Spoon: a science history podcast with Sam Kean · Sam Kean, Bleav

Human Photosynthesis

·19 min

London Zoo keeps losing lion cubs in the 1880s. Their bones soften, their legs bow, and one cub grows so weak that she can hardly move. Dr. John Bland Sutton, moonlighting at the zoo, examines the dead animals and identifies rickets. He thinks the goat-meat diet is too lean, so he recommends fattier horse meat, ground-up bones, milk, and a little cod liver oil. The zookeepers try the new food and wait nervously. The story then widens to show that rickets had also appeared in dogs and rats, and that cod liver oil had long been used as a folk remedy. That makes diet look convincing, though not fully settled. By 1923, Eleanor Hume and Hannah Smith are running rat experiments in jars lined with sawdust. They feed the rats a diet that produces rickets, then split them into different treatments. One group gets its jar air irradiated under a mercury quartz lamp with the lid off. Another group gets the rats themselves irradiated in a wire cage. Both sets improve. That improvement seems to suggest that the air has somehow retained the cure. So they test that idea directly. An assistant blows the irradiated air out of the jars before the rats go back in. This time the untreated rats do not improve. The conclusion feels neat for a moment, and then another lab fails to reproduce it. The episode ends where good science stories often do, with a tidy answer turning out to be less tidy than it first seemed.

As heard by us

A zoo mystery becomes a clear, odd little lesson in rickets, diet, and irradiated air.

The episode starts at London Zoo in the 1880s, with lion cubs dying and the cause turning out to be rickets: soft bones, bowed limbs, and a diet built around goat meat.

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Why you'd press play

A zoo tragedy turns into a tight rickets mystery for you.

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