After the Battle of Shiloh in 1862, which left 3,000 dead and 16,000 injured, there weren’t enough medics on either side to aid the wounded. Infection wasn’t well understood at that time, and so soldiers were very prone to infections.
Many of the soldiers died due to problems that could be easily cured today. Some of the soldiers sat in the mud waiting for medics. When night fell, they realized their wounds were casting a faint light. Stranger still, those exhibiting the glowing wounds turned out to have a much better survival rate than those not.
For over a hundred years after, this mysterious phenomenon was called Angel’s Glow. In 2001, its secret was cracked. It turns out bacteria were to blame.
Photorhabdus luminescens is a type of bacteria that lives in the guts of nematodes. Nematodes hunt down insect larvae, burrow into their bodies, and then vomit the bacteria into the larvae hosts. There, the bacteria (which glow in the dark) begin producing chemicals that kill the larvae and all other microorganisms inside it.
It turns out those nematodes were to blame for Angel’s Glow and its related survival rate. The bacteria had essentially killed all other harmful infectants in the wounds which increased survival and decreased infection, and its bioluminescence had produced the strange glow effect.