This agreement preserves the entire Antarctic
continent for scientific research.
#More to explore
Amundsen, Roald • Antarctica • Arctic
Ocean • Eskimo • Henson, Matthew
• Peary, Robert E.
Police
The police are people whose job is to
make sure that citizens follow the law
and do not harm others. Police officers
work for the governments of towns,
cities, counties, states, and countries.
Police Today
The police have many tasks. First, they
patrol, or keep watch over, streets and
neighborhoods. Most police officers
patrol in cars. But sometimes they patrol
on foot, on horseback, on motorcycles,
or on bicycles. Second, police go to the
scenes of crimes and emergencies to
catch criminals and to help victims.
Third, police investigate, or study,
crimes to find out who committed
Ross Island is in the Ross Sea, just off the
coast of Antarctica. Several explorers have
used the island as a base.
BRITANNICA STUDENT ENCYCLOPEDIA Police 111
them. Police fight many types of crimes.
One of the most serious is terrorism.
(Terrorists use violence to try to affect
people’s beliefs or ways of life.)
Some police officers wear uniforms.
Others work in everyday clothing, called
plain clothes. Many police officers carry
handcuffs, a notebook, and a two-way
radio. Some also carry a handgun. Some
use a stun gun or pepper spray to stop
criminals without seriously harming
them. Some officers travel with specially
trained police dogs.
Police officers whose main job is investigating
crimes are called detectives.
Detectives usually work in plain clothes.
They talk to witnesses, or people who
may know something about the crimes.
They also talk to suspects, or people
they think may be guilty of the crimes.
Detectives sometimes use hidden microphones
or cameras to record the conversations
and actions of suspects.
At the scene of a crime, detectives look
for evidence, or clues to help them figure
out who committed the crime. Evidence
includes fingerprints, footprints,
bits of cloth, blood, hair, and anything
else that the criminal may have left
behind. When they find the person who
they think committed the crime, they
arrest that person. The person may then
be put on trial to determine if they did
commit the crime. During the trial, the
detectives and other police officers often
talk about the evidence they gathered
when they were investigating the crime.
History
Ancient peoples, including the Sumerians,
the Egyptians, and the Babylonians,
had police forces. Their job was
mostly to make sure that the people
followed the rulers’ orders. Emperor
Augustus of Rome put together a large
and well-organized police force in 7 BC.
Police officers block off a street in London,
England, while they investigate terrorist
attacks.
A police officer at a crime scene
brushes powder on a door in the
hope of finding fingerprints.
Police use fingerprints to identify
criminals.
112 Police BRITANNICA STUDENT ENCYCLOPEDIA
Over the centuries other cities and
countries set up police forces.
By the 1800s police were using many
modern tools and methods to do their
jobs. Police first used telephones in
Washington, D.C., in 1878. Fingerprinting
was introduced in the 1890s.
Police first rode in cars in the United
States in 1899. In the 1920s police
started using ballistics—the study of
bullets to match them to the gun that
fired them. In the 1930s police began
using small two-way radios to communicate
with each other. Today police
depend on computers to keep records
and to search for information while solving
crimes.
#More to explore
Crime • Government • Law
Polio
Polio, called poliomyelitis in full, is a
disease caused by a tiny germ called a
virus. In the past, polio attacked many
children and left them paralyzed, or
unable to move their muscles.
The first symptoms, or signs, of polio
can be very mild. In fact, many people
who get the disease feel fine. Others
think they have caught a cold. In serious
cases people complain of having pains in
their neck, back, and legs. The pains are
a sign that the polio virus has attacked
the spine. The spine has nerves that control
the muscles of the body. If the virus
damages those nerves, the muscles
become weak.
Some people recover their muscle
strength.Others become permanently
paralyzed. If the virus damages the nerves
controlling the leg muscles, the person
can no longer walk. If the virus attacks
the nerves controlling the lungs, the
person cannot breathe without the help
of a machine. There is no cure for polio.
As recently as the 1950s polio affected
thousands of people in the United
States. Polio affected mostly children,
but some adults got it as well. The U.S.
president Franklin D. Roosevelt was
paralyzed by polio as an adult.
In the early 1950s the medical researcher
Jonas Salk made a substance called a
vaccine to protect people from the virus
that causes polio. Polio has disappeared
from most countries because almost
every child is vaccinated.
#More to explore
Disease, Human • Salk, Jonas • Virus
A child wears a brace on a leg
that has been affected by polio.
BRITANNICA STUDENT ENCYCLOPEDIA Polio 113
Political Party
Political parties are groups of people that
