transmitting malaria, would have a
chance to reecho Adam's cowardly evasion in the Garden of Eden, "It was
the woman that thou gavest me." Both sexes of mosquitoes under ordinary
conditions are vegetable feeders, living upon the juices of plants. But
when the female has thrown upon her the tremendous task of ripening and
preparing her eggs for deposition, she requires a meal of blood--which
may be a comfort to our vegetarian friends, or it may not. Either she
requires a meal of blood to nerve her up to her criminal deed, or, when
she has some real work to do, she has to have some real food.

The mosquito-brigade have still another method of checking the spread of
malaria, at first sight almost a whimsical one,--no less than screening
the patient. The mosquito, of course, criminal as she is, does not hatch
the parasites _de novo_ in her own body, but simply sucks them up in a
meal of blood from some previous victim. Hence by careful screening of
every known case of malaria, mosquitoes are prevented from becoming
infected and transmitting the disease. Instead of the screens protecting
the victims from the mosquitoes, they protect the mosquitoes against the
victim.

This explains why hunters, trappers, and Indians may range a region for
years, without once suffering from malaria, while as soon as settlers
begin to come in in considerable numbers, it becomes highly malarious.
It had to be infected by the coming of a case of the disease.

The notorious prevalence of malaria on the frontier is due to the
introduction of the plasmodium into a region swarming with mosquitoes,
where there are few window-screens or two-story houses.

No known race has any real immunity against malaria. The negro and other
colored races, it is true, are far less susceptible; but this we now
know applies only to adults, as the studies of Koch in Africa showed
that a large percentage of negro children had the plasmodium in their
blood. No small percentage of them die of malaria, but those who recover
acquire a certain degree of immunity. Possibly they may be able to
acquire this immunity more easily and with less fatality than the white
race, but this is the extent of their superiority in this regard. The
negro races probably represent the survivors of primitive men, who were
too unenterprising to get away from the tropics, and have had to adjust
themselves as best they might.

The serious injury wrought in the body by malaria is a household wo