What is Animal Magnetism?


You might have used the term “animal magnetism” to describe the je ne sais quoi that allows only a lucky few people to consistently charm the pants off their audiences, literally or figuratively.

According to the term’s 18th-century inventor, animal magnetism is a very real thing that exists in all of us as a magnetized liquid—one that empowers us, of course, but that can also form dangerous clots that will give your cosmic alignment the spins.

To understand the theory of animal magnetism, its cultural impact, and just how the latter managed to be so big, we’ll start with a quick time-and-space hop to where the pseudoscientific craze really caught on: pre-revolutionary Paris.


It was the turn of the swingin’ 1770s. The French (in large majority) were suffering under worsening food shortages and a growing financial crisis; Marie Antoinette was spending ever more time fabulously entertaining guests at the Petit Trianon in Versailles (her favorite niche in a palace that employed 10,000 for upkeep); French fashions, architecture, furniture, and writings were taking the continent by tempête.

The curtains were also coming down on the Enlightenment era, much of which found its legs in the cafes, salons, and clubhouses of the French capital. Critic Stephen Jay Gould points out that, when it came to brand new ideas, Paris was “the most 'open' and vibrant capital of Europe” at the time—a city that “[embraced] intellectual ferment of the highest order combined with quackery at its most abject: Voltaire among the fortune tellers; Benjamin Franklin surrounded by astrologers; Antoine Lavoisier amidst the spiritualists."

Enter German physician Franz Anton Mesmer, who’d left Vienna (where he’d been in hot water over failing to cure—and likely seducing—a young, blind pianist) and traveled to Paris in 1778 with his distinctive charm, private money, and seemingly innovative ideas in tow.


Prior to his arrival in Paris, Mesmer had already mostly developed his grand theory, which, “insofar as one can find coherence in his ideas at all,” Gould says, “claimed that a single (and subtle) fluid pervaded the universe, uniting and connecting all bodies." This unifying fluid had different names depending on its context: the planets orbited according to its force in the form of gravity, its manifestation as simple magnetism determined a compass’ course, and, as the fluid that flowed in all living things, it was called “animal magnetism.”

While this “subtle” fluid couldn’t actually be extracted and studied, it was thought to nevertheless affect the human body in a big way. Mesmer argued that blockages in a person’s magnetic flow could cause any number of diseases and conditions, ranging from the physical and the psychological to the simply intangible (many of his disciples also later suggested these blockages were the only cause of illness).

To remedy magnetic imbalances and blockages, Mesmer and subsequent trained practitioners (or “mesmerists”) treated patients in several different ways. In a one-on-one session, Mesmer would locate the magnetic “poles” on a person’s body (something he could do thanks to his own “unusually strong magnetism,” Gould says). He would then touch, hold, or massage the parts of the patient’s body that contained those poles in order to discharge excess energy and/or restore balance—often while staring deeply into her eyes (most of his patients were women, but not all). In some cases, he’d prescribe his patients to drink “magnetized” water that contained iron filings, or pass magnets over their bodies.

He also developed cost-effective group treatments for righting personal magnetic imbalances en masse. In a salon setting, Mesmer would instruct as many as 20 people to each take a thin metal rod from a baquet (or vat) of supposedly magnetized water—sometimes garnished with metal shavings—and pass it over their body’s poles. If the gathering were larger than 20, Gould reports, he’d “loop a rope from those who surrounded the baquet (and held the iron rods) to others in the room [...and] then instruct the roped group to form a ‘mesmeric chain’ by holding a neighbor’s left thumb between their own right thumb and forefinger,” thereby letting magnetic impulses flow through the entire linked group.

Not to be accused of only using his treatment for profit among the wealthy, Mesmer also reportedly “magnetized” a number of trees so that lower-class sufferers of illness could touch them at their leisure and discharge any surplus magnetism.


There are many semi-documented cases (mostly by Mesmer himself) of patients who seemed to recover after receiving mesmeric treatments. However, science-minded individuals at the time and in the centuries since have suggested that any positive effects from his services should be credited not to magnetism but rather to psychological means, i.e. psychosomatic healing through the power of suggestion. Dr. Mesmer certainly seemed to encourage this, using not just his palpable charm but also well-placed mirrors and “music played on the ethereal tones of a glass harmonica, the instrument that Benjamin Franklin had developed," to heighten the effect.

Mesmerism definitely had an observable impact, though. After receiving treatment, some patients (mostly women) would enter a frenzied state, flailing and moaning as their bodies’ animal magnetism levels redistributed. Mesmer encouraged this, and even provided softly furnished “crisis rooms” where guests—delivered there by a team of assistants—could comfortably work through their mesmeric fits. It was this sort of joyous, freeing hysteria brought on by mesmeric treatments that also led a good portion of Mesmer’s many critics to suspect his practice of promoting a very unseemly, unbridled female sexuality that just wouldn’t do (that, and all the knee-cupping).

Ultimately, two commissions appointed by King Louis XVI unequivocally rejected the science of Mesmer’s animal magnetism (with Benjamin Franklin, inventor of the glass harmonica, sternly sitting on the second), and the practice had effectively faded away in France by the end of the decade. The infection had already taken hold, however, and dedicated mesmerists continued touting the benefits of well-managed animal magnetism elsewhere in Europe ‘til the early 1850s.


Gould points out that "wrenching a person from his own time and judging him by modern standards and categories" isn't particularly fair or useful, especially when taking into account the fact that "the lines between science and pseudoscience were not so clearly drawn in Mesmer's time." Due to few records on the German doctor having survived, we just don't know "whether he was a simple charlatan, purveying conscious fakery for fame and profit, or a sincere believer, deluded no less than his patients."

Mesmerism’s also had lasting benefits and worth to scholars in various disciplines as either a forerunner, a counter-balance, or simply a case study; it’s provided food for thought for a wide range of philosophers, historians, and psychologists, and even led to the development of a statistically more useful practice that lives on today: hypnotism.

And if, despite generations of naysayers throughout the sciences, you’re still intrigued enough by the idea to want to try it out, there’s probably no harm in linking thumbs with friends, touching trees, or getting a particularly magnetic pal to massage your knees; stay away from the iron-filing cocktails, though.

Big Questions
Do Bacteria Have Bacteria?

Drew Smith:

Do bacteria have bacteria? Yes.

We know that bacteria range in size from 0.2 micrometers to nearly one millimeter. That’s more than a thousand-fold difference, easily enough to accommodate a small bacterium inside a larger one.

Nothing forbids bacteria from invading other bacteria, and in biology, that which is not forbidden is inevitable.

We have at least one example: Like many mealybugs, Planococcus citri has a bacterial endosymbiont, in this case the β-proteobacterium Tremblaya princeps. And this endosymbiont in turn has the γ-proteobacterium Moranella endobia living inside it. See for yourself:

Fluorescent In-Situ Hybridization confirming that intrabacterial symbionts reside inside Tremblaya cells in (A) M. hirsutus and (B) P. marginatus mealybugs. Tremblaya cells are in green, and γ-proteobacterial symbionts are in red. (Scale bar: 10 μm.)
Fluorescent In-Situ Hybridization confirming that intrabacterial symbionts reside inside Tremblaya cells in (A) M. hirsutus and (B) P. marginatus mealybugs. Tremblaya cells are in green, and γ-proteobacterial symbionts are in red. (Scale bar: 10 μm.)

I don’t know of examples of free-living bacteria hosting other bacteria within them, but that reflects either my ignorance or the likelihood that we haven’t looked hard enough for them. I’m sure they are out there.

Most (not all) scientists studying the origin of eukaryotic cells believe that they are descended from Archaea.

All scientists accept that the mitochondria which live inside eukaryotic cells are descendants of invasive alpha-proteobacteria. What’s not clear is whether archeal cells became eukaryotic in nature—that is, acquired internal membranes and transport systems—before or after acquiring mitochondria. The two scenarios can be sketched out like this:

The two hypotheses on the origin of eukaryotes:

(A) Archaezoan hypothesis.

(B) Symbiotic hypothesis.

The shapes within the eukaryotic cell denote the nucleus, the endomembrane system, and the cytoskeleton. The irregular gray shape denotes a putative wall-less archaeon that could have been the host of the alpha-proteobacterial endosymbiont, whereas the oblong red shape denotes a typical archaeon with a cell wall. A: archaea; B: bacteria; E: eukaryote; LUCA: last universal common ancestor of cellular life forms; LECA: last eukaryotic common ancestor; E-arch: putative archaezoan (primitive amitochondrial eukaryote); E-mit: primitive mitochondrial eukaryote; alpha:alpha-proteobacterium, ancestor of the mitochondrion.

The Archaezoan hypothesis has been given a bit of a boost by the discovery of Lokiarcheota. This complex Archaean has genes for phagocytosis, intracellular membrane formation and intracellular transport and signaling—hallmark activities of eukaryotic cells. The Lokiarcheotan genes are clearly related to eukaryotic genes, indicating a common origin.

Bacteria-within-bacteria is not only not a crazy idea, it probably accounts for the origin of Eucarya, and thus our own species.

We don’t know how common this arrangement is—we mostly study bacteria these days by sequencing their DNA. This is great for detecting uncultivatable species (which are 99 percent of them), but doesn’t tell us whether they are free-living or are some kind of symbiont. For that, someone would have to spend a lot of time prepping environmental samples for close examination by microscopic methods, a tedious project indeed. But one well worth doing, as it may shed more light on the history of life—which is often a history of conflict turned to cooperation. That’s a story which never gets old or stale.

This post originally appeared on Quora. Click here to view.

Big Questions
Why Do Cats 'Blep'?

As pet owners are well aware, cats are inscrutable creatures. They hiss at bare walls. They invite petting and then answer with scratching ingratitude. Their eyes are wandering globes of murky motivations.

Sometimes, you may catch your cat staring off into the abyss with his or her tongue lolling out of their mouth. This cartoonish expression, which is atypical of a cat’s normally regal air, has been identified as a “blep” by internet cat photo connoisseurs. An example:

Cunning as they are, cats probably don’t have the self-awareness to realize how charming this is. So why do cats really blep?

In a piece for Inverse, cat consultant Amy Shojai expressed the belief that a blep could be associated with the Flehmen response, which describes the act of a cat “smelling” their environment with their tongue. As a cat pants with his or her mouth open, pheromones are collected and passed along to the vomeronasal organ on the roof of their mouth. This typically happens when cats want to learn more about other cats or intriguing scents, like your dirty socks.

While the Flehmen response might precede a blep, it is not precisely a blep. That involves the cat’s mouth being closed while the tongue hangs out listlessly.

Ingrid Johnson, a certified cat behavior consultant through the International Association of Animal Behavior Consultants and the owner of Fundamentally Feline, tells Mental Floss that cat bleps may have several other plausible explanations. “It’s likely they don’t feel it or even realize they’re doing it,” she says. “One reason for that might be that they’re on medication that causes relaxation. Something for anxiety or stress or a muscle relaxer would do it.”

A photo of a cat sticking its tongue out

If the cat isn’t sedated and unfurling their tongue because they’re high, then it’s possible that an anatomic cause is behind a blep: Johnson says she’s seen several cats display their tongues after having teeth extracted for health reasons. “Canine teeth help keep the tongue in place, so this would be a more common behavior for cats missing teeth, particularly on the bottom.”

A blep might even be breed-specific. Persians, which have been bred to have flat faces, might dangle their tongues because they lack the real estate to store it. “I see it a lot with Persians because there’s just no room to tuck it back in,” Johnson says. A cat may also simply have a Gene Simmons-sized tongue that gets caught on their incisors during a grooming session, leading to repeated bleps.

Whatever the origin, bleps are generally no cause for concern unless they’re doing it on a regular basis. That could be sign of an oral problem with their gums or teeth, prompting an evaluation by a veterinarian. Otherwise, a blep can either be admired—or retracted with a gentle prod of the tongue (provided your cat puts up with that kind of nonsense). “They might put up with touching their tongue, or they may bite or swipe at you,” Johnson says. “It depends on the temperament of the cat.” Considering the possible wrath involved, it may be best to let them blep in peace.

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