as turtles’ shells, cows’ horns, and gourds.
Male chickens are called roosters. They do
not lay eggs.
94 Chicken BRITANNICA STUDENT ENCYCLOPEDIA
black, or other colors. Female chickens
are called hens. Hens are usually brown
or white. Both males and females have
one or two wattles. A wattle is skin that
hangs from the throat. Male and female
chickens also have a comb, which is skin
that sticks up from the top of the head.
Farmers usually keep chickens inside
large, modern buildings. They feed the
birds corn and other grains. Some farmers
allow their chickens to roam free
outdoors. These chickens usually roost,
or sleep, inside at night.
Hens can lay more than 200 eggs a year.
If a hen mates with a rooster before laying
eggs, the eggs will be fertilized. This
means that they will develop into chicks.
But hens can lay eggs without mating.
These unfertilized eggs are the eggs that
people eat.
Wild birds called jungle fowl are the
ancestors of chickens. Jungle fowl
belong to the pheasant family. They live
in parts of Asia, including India. Jungle
fowl eat seeds, fruit, and insects. They
fly into trees to escape from predators.
#More to explore
Bird • Egg • Poultry
Chicken Pox
One of the most common diseases of
childhood is chicken pox. Although
most people contract it between the ages
of 2 and 6, chicken pox can strike at any
age. It is a fairly mild illness in children,
but it can be serious in adults.
The first symptoms, or signs of the disease,
include a slight fever, runny nose,
and mild cough. The person will not feel
hungry and may also have headaches
and feel tired.
Roughly two weeks after being exposed
to the virus that causes the disease, red
spots appear on the face and body. These
spots are filled with fluid, and they itch
terribly. Eventually the spots form scabs,
which soon fall off.
People with chicken pox should try not
to scratch the spots. The itching can be
relieved by using medications such as
calamine lotion. It is important to keep
the spots clean.
It is extremely important to never use
aspirin to treat the headaches and body
aches that accompany chicken pox.
Using aspirin to treat chicken pox has
been connected to the development of a
severe disease called Reye’s syndrome.
A case of chicken pox generally lasts
from a week to 10 days. Because chicken
The virus that
causes chicken
pox stays in
the body after
the disease
goes away. It
can break out
years later as
a disease
called
shingles.
Itchy, red spots on the face and body are a
sign of chicken pox.
BRITANNICA STUDENT ENCYCLOPEDIA Chicken Pox 95
pox is easily passed from one person to
another, it is important for a person
with the disease to remain in bed until
the scabs have fallen off. Scientists developed
a chicken pox vaccine, or substance
that protects people from getting the
disease, in the late 20th century.
#More to explore
Reye’s Syndrome • Vaccine
Child
Development
People live much longer than most other
animals, so human childhood also lasts a
long time. Unlike baby animals, human
children need many years to learn how
to live on their own as adults. As children’s
bodies grow, so do their minds.
This growth is called child development.
People who study child development
learn how children change, from the
time they are infants until they become
teenagers, or adolescents.
There are several stages of child development.
Babies go from being infants to
toddlers to preschoolers. Then they
enter school at 5 or 6 years old. At
around 9, children are called preadolescents,
or preteens. This last stage continues
until a child becomes a teenager.
Infancy
Infancy is the most helpless stage of a
human being’s life. It takes an infant
about three months just to grow strong
enough to hold up its head. As their
muscle strength increases, babies can do
more. Over their first year infants gradually
learn to roll over, sit up, crawl, and
take their first steps with someone helping
them. They become better at using
their hands to grasp and hold things. As
they grow out of infancy, babies begin to
make sounds similar to words.
Infants enjoy holding and looking at toys
and other objects.
Children learning to walk need support to
help them keep their balance.
96 Child Development BRITANNICA STUDENT ENCYCLOPEDIA
Toddlerhood
The toddler stage begins when a baby
starts to walk, usually at about age 1.
Most children also start saying words at
about this time. As toddlers grow they
become stronger and have more control
of their bodies. Their thinking skills also
improve. They slowly start putting
words together to make sentences. They
like to copy what other people say and
do.
Preschool Age
Between ages 3 and 5, children are in
the preschool stage. Children learn
many important skills during this stage.
They learn to share and to take turns.
They learn how to play simple games
with rules, such as tag. Playing with
others helps them learn how to get along
with all kinds of people.
School Age
Starting school marks a new stage. Children’s
minds develop quickly as they
learn reading, writing, and arithmetic.
They also learn more about cooperating
with others. As their bodies grow stronger
