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Investigating Slime
In the book you read:
“Slime is the sticky essence of a gastropod’s soul, the medium
for everything in its life; locomotion, defense, healing, courting,
mating and egg protection. Nearly one-third of my snail’s daily
energy went into slime production.”
—Page 71, The Sound of a Wild Snail Eating, Elisabeth Tova
Bailey (Algonquin Books/Workman)
You can investigate the purpose of slime—
or mucus—by using your own.
Here’s a simple experiment:
Safety Precaution: Because your
mucus is a body fluid, you must be
very careful to clean your hands, your
equipment and your station to
prevent the spread of germs.
Engage: Begin by brainstorming. Where in your body would you find mucus? What is its purpose?
Explore: Find two very smooth stones of the same type or two identical pieces of ceramic tile. Using
droppers, place one drop of water on the first, one drop of your own mucus on the second.
With a stopwatch, measure the time it takes for each drop to evaporate. Create a graph to show your
results.
Wash your hands, your tiles or rocks, your droppers and your work surface with soap and water.
Explain: Mucus is found along the entire lining of
your digestive system, but is especially thick in the
mouth and stomach.
What is the purpose of mucus in the mouth?
What is the purpose of mucus in the stomach?
What is the purpose of mucus in your respiratory system (nose, bronchial tubes and lungs)?
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Extend: A different form of polysaccharide similar to mucus is found in tears. Is the purpose the same?
Many people who have had radiation therapy to tissues that should produce mucus find that they have
very dry mouths after the therapy. Given what you know of mucus, what additional health problems
might these people have?
People with “dry mouth” often use the commercial product Biotene™. Repeat your experiment,
comparing mucus, water and the commercial product. Is the effect the same?
Some people are afflicted with a genetic disease called cystic fibrosis, or mucoviscidosis. Investigate the
relationship of this disease to mucus production and what its effects are:
Evaluate: Snails have mucus on the outside of their body, as well as inside their digestive system. Use a
VENN diagram to compare the purposes of mucus in a snail and in a mammal.
Teacher Notes: Mucus is a solution of (~90 percent) water and an oligosaccharide (a form of
carbohydrate sometimes combined with a protein.) In the most general sense, mucus serves the
purpose of making water “wetter.” In chemical terms, it forms weak, temporary bonds within solution
raising the energy needed for evaporation. Because mucus increases the cohesive forces in a solution, it
raises the energy necessary for the water molecules to evaporate. So comparing similar volumes of
mucus and water, the water will evaporate more quickly.
In the most general terms, mucus is a protective coating for those cells in an animal that are exposed to
air. Cells must remain wet and maintain a specific water content in order to function. The mucus helps
make that happen. So it protects cells on the surface of a tissue from dehydration. It also helps some
cells (like those of the stomach lining) resist the effects of acids in solution. In many animals like the snail
mucus has other functions, including locomotion and signaling. Both snails and whales blow mucus
bubbles as a defense mechanism.
Snails have several forms of mucus. Each has a different consistency and chemical formula. While all are
protective, the snail also has specific “recipes” for the secretions to make it slip easily in its environment,
to attract and achieve mating, and to send chemical signals to other snails. Thick mucus helps the snail
adhere to surfaces as it climbs. Thinner mucus forms their signaling bubbles.
When students do a VENN diagram of similarities between human and snail mucus, they may reflect
their experience with oral or nasal mucus which is relatively low in viscosity. However, the mucus in
human stomachs is much more viscous and that in tear much less so. Students might also reflect on
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changes in mucus that occur during the cycle of a common cold—very thin at the height of the cold, and
thicker if a follow-up respiratory infection occurs. They might also investigate the genetic disease cystic
fibrosis, which is characterized by thick mucus and progressive damage to the respirator organs. The
formal name of the disease, mucoviscidosis, conveys the effects of the body’s failure to regulate the
viscosity of vital mucus products.