young, or foal.Within a few hours after
birth, a healthy foal is on its feet. Horses
usually live between 20 and 35 years,
but some have survived past age 40.
Horses and Humans
People hunted horses until they learned
to tame them. Scientists believe that
people first tamed horses in central Asia,
probably long before 2000 BC.
Warhorses
Ancient people used horses in wars. By
about 1,600 BC people in southwestern
Asia were fighting on horseback. They
also fought in chariots, which were
wheeled vehicles pulled by horses. About
800 years later Asians brought horses to
Europe. The army of ancient Rome
included troops on horseback.
During the Middle Ages (AD 500 to
1500) warriors called knights rode heavy
horses. When warriors stopped wearing
armor, they switched to lighter and
faster horses.
Workhorses
At first horses could not pull heavy loads
without hurting themselves. Then, in
the 1100s, people started using padded
horse collars. A horse with a collar could
pull a plow. Horses also pulled railroad
cars and other vehicles. Horses were a
major source of power until the 1900s,
when machines took over the work.
Horses in Sports
Horse racing is an ancient sport. As early
as 700 BC the Olympic Games of
ancient Greece featured horse races.
Today horses race on oval tracks or
straight courses. Some courses have
obstacles that the horse must jump over.
In harness racing the horse pulls a twowheeled
vehicle with a driver.
Horses and riders also compete in jumping
or riding sports known as equestrian
events. The Olympic Games feature
equestrian events. Other sports that use
horses include polo and rodeo.
#More to explore
Hoof • Knight • Mammal • Sports
• War
Hospital
A hospital is a place where people go for
medical attention and treatment. Someone
needing help for a serious illness or
injury may go to a hospital.Women also
go to hospitals to have babies. People
may stay in a hospital for a few hours or
for many days.
The Kentucky Derby is the most important
Thoroughbred horse race in the United
States.
BRITANNICA STUDENT ENCYCLOPEDIA Hospital 87
Types of Hospitals
General hospitals handle most medical
problems. Special hospitals focus on
certain diseases, such as cancer. Others
care for specific groups, such as older
people or people with mental illnesses.
Medical schools run teaching hospitals
to train doctors.
Religious and educational groups own
many hospitals in the United States and
Canada. They do not keep any money
made by the hospital. Some U.S. hospitals
are owned by companies that do try
to make money. Governments own and
run most hospitals in the rest of the
world.
Hospital Divisions
Most hospitals are divided into areas
with different purposes. The emergency
room handles sudden illnesses and injuries.
Patients with breathing problems or
bad burns go to the intensive care unit.
For surgery, patients go to an operating
room.Women having babies go to the
labor and delivery department. The
laboratory does medical tests. The pharmacy
prepares medicines.
Doctors guide the care of hospital
patients. Nurses follow doctors’ instructions
and make patients comfortable.
History
In the 400s BC Hindus in what is now
Sri Lanka created the first known hospitals.
The ancient Romans also treated
patients in hospitals. Christians later
created many hospitals in Europe. The
first medical hospital in the United
States was founded in 1751. It treated
mainly poor people.
As medicine got better, more middleclass
and wealthy people went to hospitals.
Today most people in developed
countries are born in a hospital, and
many die in one.
..More to explore
Disease, Human • Medicine • Nursing
• Surgery
Houston
Population
(2000 census),
city, 1,953,631;
(2007 estimate)
2,208,180
Houston is the largest city in the U.S.
state of Texas. It is also the fourth largest
city in the United States. The city owes
A girl greets her newborn sister in the nursery
of a hospital.
88 Houston BRITANNICA STUDENT ENCYCLOPEDIA
much of its growth to its large oil and
natural gas industries.
The Lyndon B. Johnson Space Center in
Houston is home base for U.S. astronauts.
The center controls space flights
and does research for the National Aeronautics
and Space Administration
(NASA).
Several large oil and energy companies
have headquarters in the Houston area.
Many factories in the city process oil
into gasoline, diesel fuel, and chemicals.
Houston is the second busiest port in
the United States. Ships reach the city
from the Gulf of Mexico through a
waterway called the Houston Ship
Channel.
Health care also fuels the Houston
economy. The Texas Medical Center is
one of the largest medical centers in the
United States.
Houston was founded in 1836, the year
that Texas won its independence from
Mexico. It was named for Sam Houston,
a hero of Texas’ war for independence.
#More to explore
Texas
Huang He
The Huang He is the second longest
river in China. (The Yangtze River is the
longest.) The name Huang He means
“Yellow River” in Chinese. The river got
its name from the color of its muddy
waters. A great Chinese civilization
developed along its banks by about the
1700s BC.
The Huang He is 3,395 miles (5,464
