to cross even low mountains. Therefore
mountain ranges tend to divide the
people on either side of them. They
often form borders between countries.
Life is hard in mountain lands. The high
places of the world are cold and have
little soil, making farming difficult.
However, many mountain areas are
vacation resorts. Skiing and climbing are
popular mountain sports.
#More to explore
Fuji, Mount • Himalayas • Kilimanjaro,
Hiking is a popular mountain sport. Mount • Plate Tectonics • Volcano
Earth’s highest
mountain is
Mount Everest.
It is in the
Himalayas, on
the border
between
Nepal and
China. It is
29,035 feet
(8,850 meters)
high.
BRITANNICA STUDENT ENCYCLOPEDIA Mountain 195
Mount Olympus
#see Olympus, Mount.
Mouse
Mice are small, gnawing mammals that
belong to the rodent family. They can be
found almost everywhere in the world.
In many countries they are the most
common animal.
There are 38 species, or types, of mouse.
The most commonly known is the
house mouse. It is most often found in
buildings. The house mouse grows to
about 8 inches (20 centimeters) long
from its nose to the tip of its tail. It has a
scaly tail that is about half as long as its
body. Its fur is brown or gray.
Mice live mainly on the ground and are
active at night. Some types are good
climbers while others are strong swimmers.
They use their senses of smell and
hearing to find their way around. House
mice build their nests in hidden spots
near food. Mice eat almost anything,
including seeds, grains, and insects.
Sometimes they eat human foods.
It takes about three weeks for a litter of
house mice to be born. Each litter has
about 1 to 18 young. A pair of mice can
give birth to 30 or 40 babies a year, even
more if food is plentiful.
Mice are often considered pests. They
can destroy food supplies and gnaw
holes in homes. They also can spread
disease. However, some people keep
mice as pets.
#More to explore
Mammal • Rodent
Mouth
In most animals, food enters the body
through the mouth. The mouth is the
opening to the digestive system. The
digestive system is a group of body parts
that breaks down food into fuel for the
body.
In humans and many other animals, the
mouth is the place where food is chewed
and mixed with a clear liquid called
saliva. The mouth is a way for air to
enter the body, too. Human beings also
use their mouths for speaking and for
making facial expressions.
The Human Mouth
The human mouth includes several
parts. The lips surround the outside
edge of the mouth. The cheeks form the
sides of the mouth, and the floor forms
the bottom. Saliva enters the mouth
through small tubes in the floor and the
cheeks. The roof is the top of the
mouth. It has two parts. The part in
front is bone covered by flesh. The part
in back is soft flesh. A small piece of
flesh called the uvula hangs from the
roof of the mouth in back.
The house mouse is a well-known type of
mouse.
196 Mount Olympus BRITANNICA STUDENT ENCYCLOPEDIA
Behind the lips, two sets of teeth grow
from the top and the bottom of the
mouth. A person uses the teeth to chew
food before swallowing it. Gums surround
the teeth and connect them to the
jawbone. The tongue helps to control
food while chewing and to make sounds
for speech.
Mouths of Other Animals
Animals have many different mouth
shapes and structures. These different
types of mouths allow each type of animal
to eat a certain diet. Anteaters have
small, tube-shaped mouths with no
teeth. They use their long tongues to
lick up insects. A hard beak surrounds
the mouth of a bird. Insects have special
features called mouthparts near their
mouths. Grasshoppers have jaws for
chewing plants as well as mouthparts
that hold food in place. Butterflies and
moths have tubelike mouthparts to suck
food into the mouth.
#More to explore
Digestive System • Teeth • Tongue
Movie
Movies are a form of entertainment that
is popular all over the world. Movies are
pictures that seem to move when shown
on a screen. They are also called motion
pictures or films.
Equipment
Making and viewing a movie requires
special equipment. Two important
pieces of equipment are the movie camera
and the movie projector.
A movie camera records photographs, or
pictures, on film. A movie camera takes
many still pictures very quickly. Most
movie cameras take 24 pictures every
second. Because they are taken so close
Humans take in air and food through the
mouth.
Many people work together to make a movie.
BRITANNICA STUDENT ENCYCLOPEDIA Movie 197
together they catch very small differences
in movement.
A movie projector makes the still pictures
appear to move. As film runs
through it, a projector flashes the pictures
one after the other on a screen.
The pictures go past the eye so quickly
that the brain links them together as a
moving scene.
The projector also plays the movie’s
sound track. The sound track contains
all of the sounds of the movie, including
talking, music, and sound effects. The
sound track is a thin band that runs
along the edge of the film, next to the
pictures.
Movie theaters receive reels of film. A
typical film is five or six reels long. Theaters
usually join the reels together to
