Human Skull Moss – “Usnea”

By the end of this post, you are likely to know more than you ever thought you would about an extremely coveted medical treatment popularized in Early Modern Europe: Human Skull Moss, aka “usnea”.

It was made up of exactly what it sounds like — you can see an example here from the Berlin Botanical Museum. Highly prized among physicians, usnea — often mixed with other substances like manure and animal fat — was used to cure a variety of ailments, many of which were associated with maladies of the head. And although the famed alchemist Paracelsus (d. 1541) noted that even the skull moss of corpses found in the street would do, other sources argue that skulls of those who had died a violent death — execution by hanging, for example — were preferred.

And so why (to us) this macabre cure? And why be picky about the way the skull’s human died? The answers come from two common medical ideas in circulation at the time. First is the notion called the “doctrine of signatures,” which had been around since Ancient Roman times but was popularized by Paracelsus — a theory that maladies had cures in plants and minerals that looked like each other. The other came from beliefs about vital forces and from whence they arose. A “moss” growing from a skull takes up the skull’s force, for instance. But there was also a widespread belief that when someone died a violent death, their life-force stuck around for a longer time.

It turns out that “usnea” is the name of a genus of lichen (see second image) with hundreds of species, and WebMD says it does have medicinal properties. It looks a bit like Spanish Moss, though, so don’t go recklessly foraging. And you can buy droplets of it in herbal tinctures (slide three), which might make better Halloween gifts than the often grandiose curative claims that its advertisers promote.