(9)
the parasite, called sporozoites, are produced, which become
lodged in the salivary or poison gland and duct of the mosquito.
(6) When this mosquito next bites another man, some of the sporozoites
are injected into him with the salivary fluid.
(7) In his body they develop into the young parasitic animals in the red
blood cells exactly identical with the original ones.
(8) As the malarial parasite does not pass any part of its life in any
other environment than men and mosquitoes, it follows that men
and mosquitoes are the only sources of infection of malarial
fevers.
(9) It has been proved almost beyond any possible doubt that there is
no other method by which malarial fevers are contracted in
nature than by the bite of a properly infected Anopheline mos-
quito.
(10) We cannot contract malarial fevers from drinking impure water, or
from the soil, or by breathing impure air; and water and air
are only indirectly connected with malarial infection in the sense
that they are the homes of the malaria-carrying mosquitoes.