ies thousands of
people died from this every year, and doctors did not know just how it
was carried from place to place.

"Our Government appointed a commission to study the matter. Dr. Walter
Reed, a surgeon of the United States Army, with three assistants, went
to Havana and built a house, carefully screened, just like that of the
English physicians in Italy. People thought that the fever was carried
in the clothes and on the sheets of those who were ill. To prove that
this was not so, these men wore the clothes of sick people, and even
slept on the sheets taken from the sickbed. They did this disagreeable
thing for twenty days, keeping the little house very warm, and shutting
out the fresh air and sunshine. But in spite of all these things the men
continued well and strong.

"They wanted to prove even more surely that it was a certain kind of
mosquito which really did the harm. So they built another house.
Everything in this house was pure and clean. The rooms were flooded with
fresh air and sunshine. Half of the house was carefully screened and
shut off from the other half. The men in the half that was screened kept
perfectly well. Those in the other half let themselves be bitten by
mosquitoes which had been in the houses where there was yellow fever.
All became dangerously ill with the fever. Two of these brave physicians
died of the fever while trying to find the cause, in order that they
might save the lives of thousands of people."

"That is modern heroism," said Mrs. Reece, "and service of the highest
sort. All humanity is indebted to those brave men. There is no doubt but
that our Panama Canal could not be in progress to-day were it not for
the extermination of the mosquito in the canal zone. Since we can never
tell where a mosquito has been, or what kind of a mosquito it is, I
suppose it is best to keep mosquitoes from biting, and always to keep
them out of the house. And now, children, supper is ready, and after
that games. Let us go to the dining-room!"

XI

CAMPING OUT

At last the day, expected all summer long, had come. The children, Hope
and Betty, Jack, Peter, and Jimmy, Mrs. Reece and Ben Gile, were
gathered on the edge of the pond, their packs in the canoes, their
paddles at bow and stern. Other guides had taken the food and tents
ahead the day before. Their friends had gathered to bid them good-bye,
and finally, amid the farewells, they were off, Jimmie in a canoe by
himself, Jack an