him. In fact, the court said that he did
not even have the right to file a lawsuit.
The court also changed an earlier law
that had banned slavery in territories
north of Missouri. This angered people
who were against slavery. The issue of
slavery grew to be so much of a
problem that it led to war between the
states in 1861. The defeat of the South
in the American Civil War finally ended
slavery.
#More to explore
American CivilWar • Slavery • United
States Government
Drought
Wherever there is a shortage of rain over
a long period of time, there is drought.
Drought affects plants, animals, and
people. It is a serious problem for farmers
and for the people who depend on
the crops they produce.
Drought may occur almost anywhere in
the world. Deserts receive very little rain
all year. They are sometimes said to be in
a permanent drought. Places that have a
rainy season and a dry season have seasonal
drought during the dry season.
Other places can experience drought at
any time.
Drought results from changes in Earth’s
atmosphere. Some droughts are caused
by shifts in the winds that normally
bring rain to an area. Others are caused
by changing ocean currents, which
affect the temperature and moisture of
the air.
Severe droughts can last for months or
years. When this happens no crops will
grow. As a result many people and animals
may die of famine, or lack of food.
Severe droughts often force people and
animals to move to find water. Some
farmers go to places where they think
conditions will be better for their crops
Drought can
lead to dust
storms. When
soil dries out
and cracks it
can be blown
away by wind.
Dred Scott was a slave who sued for his
freedom. He did not win his court case.
BRITANNICA STUDENT ENCYCLOPEDIA Drought 77
and animals. Some people give up farming
altogether. They move to cities to
find other types of work.
#More to explore
Atmosphere • Desert • Famine
Drug
A drug is a substance that changes the
way a person’s body works. Medical
drugs can ease the symptoms of illnesses
and fight diseases. Some people also use
certain kinds of drugs for nonmedical
purposes.
How DrugsWork
Some drugs work by changing the way
cells in the body behave. For example, a
chemical in the body called histamine
causes the symptoms of allergies. Drugs
called antihistamines ease these symptoms.
The drugs do this by joining with
cells to block the histamine.
Other drugs attack living things that
invade the body—for example, bacteria
and parasites. Drugs can kill these
organisms, stop them from reproducing,
or block their effects.
Medical Drugs
Patients get drugs from doctors or from
pharmacies. Pharmacies can give certain
drugs to patients only after a doctor
orders them. Doctors’ orders for drugs
are called prescriptions. Patients can
also buy some drugs without
prescriptions—for example, aspirin and
cough syrup.
Drug manufacturers must prove that
their drugs are safe and that they work
before they can be sold. In the United
Cracked, dry dirt covers marshland in a drought region of California.
78 Drug BRITANNICA STUDENT ENCYCLOPEDIA
States the Food and Drug Administration
studies all drugs before they can be
sold there.
Illegal Drugs and Drug Abuse
Many governments around the world
have banned the use of certain drugs—
for example, marijuana, cocaine, LSD,
heroin, and Ecstasy. These illegal drugs
are generally not used as medicine.
People often take illegal drugs for fun
but ignore the harmful side effects. They
may become addicted, or unable to stop
taking the drugs. They may get sick or
even die.
Such dangerous use of illegal drugs is
called drug abuse. People can abuse legal
drugs, too. They may take medication
when they are not really sick, or they
may take too much.
History
Throughout history almost every society
has used drugs for medicine and for
rituals. Early people made drugs from
plants, animals, and minerals that they
found in nature. Eventually scientists
learned how to take different chemicals
out of those natural materials. They
studied what those chemicals did to the
body and decided which illnesses they
could treat. From those chemicals they
created drugs.
..More to explore
Bacteria • Disease, Human • Parasite
Dublin
Population
(2006 census),
city, 506,211;
urban area,
1,186,159
Dublin is the capital of Ireland, a country
in western Europe. The city lies on
the Irish Sea. The River Liffey flows
through the middle of Dublin.
Dublin is the largest city in Ireland by
far. It is also the center of Ireland’s
economy and culture. Trinity College
was founded in Dublin in 1592. It is
Ireland’s oldest university.
Dublin’s economy grew greatly in the
early 21st century. Most people in Dublin
work in service industries such as
Pain relievers, such as aspirin, are a very
popular type of drug. Store shelves are
crowded with the many different brands.
BRITANNICA STUDENT ENCYCLOPEDIA Dublin 79
tourism and banking. The city is one of
Europe’s leading producers of computer
software. Factories in Dublin make electronics,
food products, beer, and medicines.
The city is also the main port of
Ireland.
Vikings from what is now Denmark
founded Dublin in the 800s. In 1014 an
