Natural dread: Slimer from “Ghostbusters” (1984). Photo: Everett Collection Inc / Alamy Stock Photo

The weird and wonderful world of slime

Ooze plays a vitally important role in our lives—from biology to cutting-edge technology
December 9, 2021
Slime: A Natural History
Susanna Wedlich, translated by Ayça Türkoğlu
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Anyone who was a child in the 1990s will know the outsize role slime played in our early life. Think of those lazy Saturday mornings, the indolent hours every day after school spent in televisual worship. It was everywhere: poured over parents and teachers, decanted into baptismal pools for grumpy neighbours, rained down on the clueless and the over-competitive—on losers of all kinds. 

Once, on a tour of Nickelodeon Studios around 1996, I was told that their industrial quantities of green goop were actually vanilla pudding—thinned with smooth apple sauce, then dyed to create its trademark vibrant shade. Yet this knowledge did little to loosen the grip this gloop held on me—the “perverse allure,” as Susanne Wedlich puts it in her remarkable new book Slime: A Natural History, that slime has for us all.

How much do you know about slime? Or perhaps the better question is: how much do you want to know about slime? Before reading this book, I would have answered: very little, on both counts. But the charm of Wedlich’s writing is in its apparently revolting subject matter. She takes delight in the ooze, revels in the squidge, and brings it together in admirably well-organised form to create a rollicking read full of horrifying facts and disturbing anecdotes that you will be putting people off their dinner with for years to come.

The book opens with a brief cultural history of slime, exploring the roots of our aversion and how this natural dread for all things gelatinous has seen it storm popular culture—from children’s television to horror movies, Ghostbusters to Alien, the red menace of The Blob to the grotesque, beslimed rebirth of The Matrix. Our scariest stories of ghosts and assailants from outer space are, of course, plumbed from the depths of our own subconscious—and, Wedlich assures us, “at the centre of it all is slime.”

The disgust response, an instinctive emotional reaction that serves to keep us safe from harm, is a key component in the psychology of slime. Though we all experience natural disgust to some extent, it has a strong learned element—as any parent who has fished a worm from their toddler’s mouth will know—and thus the precise objects of our revulsion may be culturally specific. In surveys, British women reveal themselves to be unusually disgusted by obscene language, while those from Burkina Faso recoil from pigs, and the Dutch from fishmongers. But slime unites us all. As a common signifier of decomposition, infection, poor hygiene and spoilt food, it presents us with a simple heuristic: avoid slime and avoid illness.

Sex might be an uncommonly slimy activity, but the body has its ways. Just as water tastes better the thirstier we are, so we are better able to contain our disgust at bodily secretions when sexually aroused. Not everyone, though; the queasy Jean-Paul Sartre—despite his well-documented womanising—never lost his distaste for “le visqueux,” and railed repeatedly against the “degenerated liquid,” the “sickly-sweet, feminine revenge.” Sartre is far from the only man whose misogyny has found a focus in the apparent muculence of female genitalia (although, as this woman must object, men surely are at least as slimy during sex, if not more so). But Sartre’s sexual dysfunction was such that, as he once admitted, he preferred masturbation to the act of love itself.

Perhaps with this cautionary tale in mind, Wedlich asks us to dial down our revulsion more generally. Slime, and all things slimy, are being “forced out of our ultra-hygienic world,” she argues, even though “it’s part of our nature.” Slime, gunge, gunk and gloop play important roles in many areas of life, from biology to cutting-edge technology. There is a great deal we can learn from studying them.

“Slime” is a catch-all term that inevitably defies definition. Wedlich defines her slime as being viscoelastic matter that unites “the properties of solids and liquids.” In biological organisms this takes the form of hydrogels—that is, “water caged in a three-dimensional structure”—which faithfully serve a great number of crucial life functions. Without phlegm in our lungs and airways we could not breathe; without layers of mucus protecting our stomach linings from acid we could not feed. In the female reproductive tract, to take another example, a cervical mucus plug serves as a sort of bouncer, protecting the uterus from bacterial invasion yet allowing exclusive entry to spermatozoa during select times.

Biomedical scientists are hard at work attempting to create synthetic mucuses and other hydrogels, which might serve as wound dressings or novel forms of contraception, or be used to correct various forms of dysbiosis—when our “internal slimescapes” are thrown out of whack by pathogens. The power of hydrogels might be harnessed to create biofilters, catching microplastics in wastewater plants. Or smart hydrogels could be engineered to be “transparent, stretchable, locomotive, biocompatible, remote-controlled, weavable, wearable, self-healing and shape-morphing.” The future, as seen through Wedlich’s eyes, is slimy.

Interesting though this all is, what will knock you off your chair is how other species employ their own forms of goo. This is pure Lovecraftian body horror: we meet snails that stab each other with slime-tipped “love darts”; slugs that abseil from overhanging branches, “entangled in an elastic thread of slime”; frogs that will glue themselves to their mates’ bodies; and squid that squirt out clouds of slimy ink in their own form to confuse their enemies—creating an army of doppelgängers that will stay stable just long enough to let their creator make a quick getaway.

Elsewhere, we are introduced to the caecilian, a serpentine amphibian with vanishingly small eyes and needle-like teeth, which births live young that will slowly skin their mother alive over the course of the following weeks. There is also the pearlfish, a slender, iridescent creature that dwells inside the anus of a sea cucumber. It is a terrible house guest, over time gnawing away at the sea cucumber’s internal organs. The sea cucumber, quite reasonably, would prefer that the pearlfish didn’t; it will attempt to oust it by secreting nasty toxins, but the pearlfish can withstand these attacks thanks to its thick and slimy protective sheath.

There are carnivorous plants like the tiny sundew, which dissolves spiders in its sticky sap; or the Pisonia, the “bird catcher” tree, which affixes its gummy seed pods to passing feathers—often handicapping these couriers so thoroughly that “their bodies litter the area around the plant’s roots.” And then there is the “unassuming” shepherd’s purse, a delicate wildflower common to Britain, which kills more than 90 per cent of the insects it attracts by gluing their mouths shut and suffocating them.

Slime: A Natural History is simply oozing with repellent titbits like these, which filled me with a wicked glee. We learn about the radioactive “snottites” growing in abandoned uranium mines: stringy stalactites made of microbes that may be able to live on and even interact with dangerous nuclear waste. And how, before the transmission of disease was properly understood, certain symptoms of disease were considered somewhat aspirational; Alexandre Dumas would immortalise one of his age’s great beauties in La dame aux camélias—celebrating his lover Marie Duplessis’s rosy cheeks, shining eyes and heaving bosom not long before she passed away from tuberculosis, aged 23. (“How is it possible that a disease characterised by coughing, emaciation, relentless diarrhoea, fever, and the expectoration of phlegm and blood became not only a sign of beauty, but a fashionable disease?” asks one historian. I direct you to the heroin chic of the 1990s. Some things never change.)

“How much do you know about slime? Or perhaps the better question is: how much do you want to know about slime?”

Such vivid anecdotes come thick and fast and do much to grab the reader’s attention. But Wedlich has serious intent. Having talked us through the history of ideas as it relates to slime—beginning with the Ancient Egyptians’ belief in the spontaneous generation of life from mud, ooze and other products of putrefaction, persisting through Aristotle and into the Christian age, right up to Haeckel’s theory of primordial slime in the 19th century—she reflects on more recent findings, which have underlined the significance of our microbial ancestry.

For billions of years, microbes were the only form of life on Earth, engineering the planet to their purposes. They enriched the atmosphere with oxygen, sculpted the rock, divided every inch of this world between them. They have been, writes Wedlich, the primary engine driving the biology of this planet, with slime their enabler—“the éminence gluante,” if you will. Even today, slime in the medium of microbial mats and biofilms forms the interfaces between water, land and air, while playing fundamental roles in oxygen transfer, the transfer of energy and the stabilisation of deserts.

Should these delicate equilibriums be disturbed—by rising global temperatures, for example—who knows what might happen. The gel-like microlayer that forms “the skin of the sea” might thin, causing the de-oxygenation of the ocean. Equally, knowing microbes and their talent for survival, they might thrive. The layer might thicken. We may see yet the advent of the age of slime—a return to dominance for the microbe over the mammal, and a follow up to its earlier billion-year reign.