ially true of those who smoke
several cigarettes daily. A few years ago, when our country was at war
with Spain, thousands of young men, wanted for soldiers, were examined
to find out whether their bodies were strong enough to endure the
hardships of war. Hundreds were refused admittance to the army because
of weak bodies, and many of them were reported by the physicians as
having hearts weakened by the use of tobacco.

The boys preparing for the army at the Military Academy at West Point
and for sea fighting at the Naval Academy at Annapolis are not allowed
to smoke cigarettes. Our country must have strong men for hard work.
Tobacco never gives strength, but often causes weakness.

CHAPTER XVII

INSECTS AND HEALTH

=Malaria or Chills and Fever.=--Malaria is a disease in which the
patient usually has a chill followed by a fever at the same time each
day or every other day. Thousands of people suffer from this sickness
in the warm parts of our country and hundreds of them die every year.
In some regions people cannot live because this sickness attacks every
one who comes there.

Many years ago a doctor found in the blood of malaria patients tiny
animals. He thought that they might be the cause of the illness, but
he could not find out how they got into the blood.

=Finding out how Malaria Germs get into the Blood.=--It had been
noticed for many years that mosquitoes were always found wherever
there was malaria. In the year 1900 two men decided to find out if
they could live in a malaria region and not have the disease when the
mosquitoes were kept from biting them.

[Illustration: FIG. 73.--Position of the common humpback mosquito at
rest with body full of blood sucked by thrusting the bill into the
flesh.]

They made their home a whole season in a cottage in the midst of many
persons who were sick with malaria. They breathed the same air, ate
the same kind of food, and drank the same kind of water as those who
suffered from the disease, but they remained well. The only thing that
they did different from those who got sick was to keep the mosquitoes
out of their rooms at night by means of screens. This experiment and
many other studies have shown that we catch malaria only by the bites
of mosquitoes.

[Illustration: FIG. 74.--Position of the malaria mosquito at rest.]

=Only a Few Mosquitoes carry Malaria.=--Malaria is not common in all
regions where mosquitoes live, and it has been found that only o