Chapter V. 
PROPHYLACTIC METHODS BASED UPON THE DESTRUCTION OE 
MALARIA PLASMODIA (QUININE PROPHYLAXIS). 
It is obvious that if we can destroy or prevent the development of 
the malaria plasmodia in infected individuals we will succeed in 
preventing the disease, as it will thus be impossible for mosquitoes 
to become infected. This fact is the basis of quinine prophylaxis, 
which consists in the administration of this drug to all individuals 
harboring the plasmodia and to all those exposed to the bites of 
mosquitoes capable of transmitting the plasmodia to man. 
Perhaps no method in the prophylaxis of the malarial feA r ers has 
given rise to more controversy than the use of quinine as a prophy¬ 
lactic. Enthusiasts in its favor have claimed that the use of this 
drug alone is all that is needed to eradicate malarial infections from 
any locality, while its most violent enemies have claimed that it is 
not only practically useless but even harmful. It is evident that 
the truth must lie somewhere between these extreme opinions, and 
it is my belief that quinine prophylaxis is a most valuable method, 
but one that should not be relied upon to the exclusion of other 
methods except under conditions that render the combination with 
other methods impossible. 
From the observations of many investigators we know that quinine 
is capable of destroying the plasmodia while they are in the blood 
of man, and from clinical observation we know that this destruction 
is followed by the disappearance of the symptoms of infection 
and the recovery of the patient. In other words, quinine is a specific 
in the treatment of malaria, and to deny the efficacy of the same 
drug, when properly administered, in the prophylaxis of the same 
disease is absurd. If quinine can destroy the plasmodia after symp¬ 
toms of infection are present, it will certainly destroy them before 
they become numerous enough to cause symptoms; but experience 
has shown that enough of the drug must be given to really destroy 
the parasites, and that this means that considerable doses have to be 
taken and have to be continued just as long as the individual is ex¬ 
posed to malaria mosquitoes. 
The most ardent advocates of this method of prophylaxis, as Koch, 
have claimed that by it alone it is possible to rid a community of 
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