By Susanne Wedlich (Granta £20, 336 pp) 

In the 1960s, New York City Fire Department copied some fish.

They resemblanced predatory bony types such as the perch or barracuda. This slimy substance reduces friction between their bodies, allowing them to swim extremely fast.

The Fire Department made their own slime called Polyox and added it onto the tanks of their fire engines. Their goal was to increase the distance their water hoses could shoot water. 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)

Susanne Wedlich looks at slime in all its forms in a new book (file photo)

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

A certain black slug was used in Sweden to lubricate cart wheels until the 20th century. An abundance of the stuff would be kept onboard, and an unfortunate slug would then be placed on the wheel hub, and crushed as the journey went on.

If you were lucky, you may have come into this world as an ordinary snail who 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 Widlich interprets her brief in a wide manner. She examines slime as it appears, from prehistory all the way to today, including the stuff that gave rise life. This book is best for those who have a strong interest and knowledge 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 is completely transparent and avoids predators. Or, almost: its digestive glands are dark.

The creatures that seek the squid as their next meal tend not to hunt from the bottom, but look upwards for victims silhouetted against the light coming in from the 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 quite 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. To prevent dangerous pathogens from entering the womb, the plug thickens during pregnancy.

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

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 difficult, so are the events that lead 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 testing a similar substance, which could stop enemy vessels from moving.

Arion subfuscus is a slug that sticks to the ground with slime so strong it makes it difficult for birds to remove. 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.

GoJelly, a project that investigates the use jellyfish slime to trap microplastics within wastewater plants, in order to prevent them from reaching the oceans, is called GoJelly.

The book will be of interest to language lovers. ‘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’.