The very slimy truth about being human!

The very slimy truth about being human! Author delves into the history of slime in a new science book

  • Susanne Wedlich examines slime in its various guises in a new science book
  • New York Fire Department made a version of slime, called Polyox, in the 1960s
  • Experiment was abandoned because the firemen kept slipping over in it  



By Susanne Wedlich (Granta £20, 336 pp) 

In the 1960s, the New York City Fire Department decided to copy some fish.

Specifically, they copied predatory bony types like the perch and barracuda, which emit a slimy substance that reduces friction between their bodies and the water, allowing them to swim incredibly fast.

The Fire Department made a version of that slime, called Polyox, and added it to the tanks on their fire engines. The aim was to increase the distance over which their hoses could shoot the water. And it worked. The trouble was, it worked too well — the water displayed so little friction that the firemen kept slipping over in it. The experiment was abandoned.

Susanne Wedlich examines slime in its various guises all the way back to pre-history in a new book (file image)

It was one of the many uses to which mankind has put that disturbingly unpleasant — yet strangely fascinating —substance known as slime. As far back as ancient Rome people noticed that the yellow excretions of the banded dye-murex snail turned deep violet in bright sunshine. So thousands of the poor creatures were killed in order to dye Roman rulers’ gowns an imperial purple.

As recently as the 20th century, a certain black slug was used to lubricate the wheels on carts in Sweden. A supply would be kept on board, and whenever an axle began to squeak, an unfortunate slug would be placed on the wheel hub and crushed as the journey continued.

If you were lucky, on the other hand, you came into this world as an ordinary snail that lived near Patricia Highsmith. The novelist kept hundreds of them as pets, ‘taking them in a salad-filled handbag to dinner parties for company’.

When Highsmith moved to France, she got round an import ban by smuggling the snails into the country during several trips, ‘stowing a few of them under her bosom each time’.

Susanne Wedlich interprets her brief widely, examining slime in its various guises all the way back to pre-history, including the stuff from which life first emerged. As a result, the book is really for those with a strong interest in the natural sciences. But the lay-reader still gets some choice pickings, mostly of the ‘surely that can’t be real?’ variety.

There’s the species of squid, for example, that confuses predators by shooting out several slimy replicas of itself. Or the glass squid, which avoids the predators in the first place by being completely see-through. Or almost completely: its digestive gland is dark.

The creatures that want the squid for their next meal tend to hunt from below, looking upwards for victims silhouetted against the light coming from above.

So the digestive gland, which is long and thin, can rotate within the squid’s body — whichever way the creature is facing, the gland turns (rather like a compass needle) to leave its thin end pointing straight down. This minimises the squid’s chances of being spotted.

We humans are pretty slimy, too. There’s a double layer of the stuff lining our stomachs, to make sure that the hydrochloric acid in there to kill harmful microbes doesn’t start dissolving our own tissue.

At certain times of the month, the mucus ‘plug’ guarding the cervix becomes thinner, thereby allowing access to sperm which at other times would be blocked. Then, in pregnancy the plug thickens again, to prevent dangerous pathogens invading the womb.

SLIME: A NATURAL HISTORY By Susanne Wedlich (Granta £20, 336 pp)

The white of a hen’s egg serves the same purpose. It’s there to protect the embryo — even if a microbe got through the hard shell and the softer membrane inside, ‘crossing the albumen to get to the embryo [would be] like a journey across the Atacama Desert for humans’.

If reproduction is slimy, so too are the events leading to it. The males of some species of winkle use the slime trails of females to choose a partner: ‘Well-fed ladies with broad trails free of parasites are particularly popular’. As Wedlich points out, ‘advertisement-by-slime is helpful for slugs and snails; after all, they rarely meet by chance, and speed-dating is out of the question’.

Then there’s the African common rain frog, whose male has front legs too short to hold onto the female during mating — so he attaches himself to her back using slime instead.

It’s not only the New York City Fire Department that has taken ideas from nature.

The U.S. navy studied the hagfish (known in German as the schleimaal — slime eel), which defends itself by firing out a suffocating gel that can even cause a shark to gag. The military boffins are now trialling a similar substance that could stop enemy ships in their tracks.

The slug Arion subfuscus sticks itself to the ground with slime so strong that birds find it impossible to dislodge. Scientists analysed the goo, then used it as the starting point for a surgical glue that works in wet conditions — they’ve even used it to repair a hole in a pig’s heart.

And GoJelly is a project investigating the use of jellyfish slime to trap microplastics in wastewater plants, to prevent them reaching the sea.

Language lovers will learn something from the book. ‘Amphibian’ comes from the Greek amphi, meaning ‘both’, and bios (‘life’), because the creatures start off as herbivores living in water, before turning into carnivores that can exist on land.

But my favourite name belongs to some microbes that live in the Earth’s crust, sealed away in a coating of gel. Experts have named them ‘subsurface lithoautotrophic microbial ecosystems’ — purely so they can be termed ‘SLiMEs’.

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