In ye olden days, in the Middle Ages, European medicine revolved around the study of the four

humors, blood, phleg, yellow bile, and black bile. A person's health was said to depend on the

balance or imbalance of these four fluids in the body.

The four humors were also believed to influence a person's mood or personality.

If, say, you had too much black bile in your guts, you were likely to be gloomy and depressed,

and just sort of a bummer to be around. Like Eeyore or Professor Snape, or like anyone who

doesn't listen to podcasts about birds. An excess of blood, on the other hand, would make you a happy,

optimistic person, and so on. During roughly the same historical period, medieval naturalists

made an astonishing discovery

about the internal anatomy of pigeons and doves.

It turns out that these birds do not have a gallbladder.

It's true. Pigeons and doves do not have a gallbladder.

The gallbladder is a little storage sack for bile. Also known as gall, bile is a greenish or yellowish secretion that helps with the breakdown

and digestion of fat. Humans have a gallbladder, of course, as do a bunch of other animals.

Medieval doctors identified the gallbladder as the source of yellow bile, one of those four humors.

It was thought that when somebody's body has too much yellow bile, it makes them short-tempered and

violent. So those naturalists in the dark ages ended up connecting the dots.

They reasoned that because pigeons and doves have no gallbladder, they must produce no yellow bile.

And a lack of yellow bile would explain why these birds have such gentle, timid dispositions.

To paraphrase a 13th century monk named Bartholomeus

Anglicus, the dove is a messenger of peace, an example of simpleness, clean of kind, plenteous in

children, follower of meekness, friend of company, and a forgetter of wrongs. And here's a quote from a medieval bestiary.

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