e fully appreciated their significance. The
dreaded vomit soon appeared. I was too weak to see him again in
that condition, and there was nothing that I could do to help him.

"Dr. Lazear left a wife and two young children, one of whom he had
never seen."

These experiments and many others like them conducted on soldiers and
Spanish immigrants proved that this particular mosquito would transmit
the disease under certain conditions.

1. The mosquito must bite the patient during the first three days of the
fever; after that a yellow fever patient cannot infect a mosquito.

2. A period of twelve days must elapse before the mosquito is able to
infect another person. After that she may infect anyone she may bite;
that is, the germs remain virulent during the rest of the mosquito's
life. The French Yellow Fever Commission working in Rio de Janeiro claim
that the first generation of offspring from such an infected mosquito is
capable of causing the disease after they are fourteen days in the adult
condition.

The next step was to ascertain whether the disease could be contracted
in any other way than by the bites of infected mosquitoes. A camp named
Camp Lazear was established and the following tests made: A
mosquito-proof building of one room was completely divided by a wire
screen from floor to ceiling. In one room fifteen mosquitoes that had
previously bitten yellow fever patients and had undergone the proper
period of incubation were liberated. In this room a non-immune exposed
himself so that he was bitten by several of the insects. A little later
the same day and again the next day the mosquitoes were allowed to feed
on him for a few minutes. Five days later, the usual incubation period,
he developed yellow fever.

At the same time that he entered the building two other non-immunes
entered the other compartment where they slept for eighteen nights
separated from the mosquitoes by the wire screen. They showed no signs
of taking the fever.

In another mosquito-proof house two soldiers and a surgeon, all
non-immunes, lived for twenty-one days. From time to time they were
supplied with soiled articles of bedding, clothing, etc., direct from
the yellow fever hospital in the city. These articles had been soiled by
the urine, fecal matter and black vomit obtained from fatal and other
cases of yellow fever. These articles were handled and shaken daily, but
no disease developed among the men and at the