Modern scientists are still investigating what might be behind reports of alleged spontaneous human combustion, but by the end of the 18th century, reports of humans suddenly going up in flames were pervasive enough that physicians compiled supposed risk factors for the phenomenon.
History magazine Lapham's Quarterly offers this list of "risk factors" collected by physician Pierre Lair in 1799:
1. Victims were older, usually over 60.
2. Victims were overweight.
3. Victims led inactive lives.
4. Victims were alcoholics.
5. Women were more prone to spontaneously combust than men.
6. At the scene there was often an external flame, such as a candle or fireplace.
7. Combustion was extremely rapid.
8. The flames were difficult to extinguish.
9. The flames produced a strong empyreumatic odor.
10. The surrounding room was coated with a thick, yellow, greasy film.
11. The first usually consumed the trunk of the body, but left the head and extremities intact.
12. Accidents occurred during fair weather, and more often in winter than in summer.
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