(1973) n°3 - Royal Academy for Overseas Sciences

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SAMENVATTING
De ontdekking van de volledige cyclus van de menselijke Plasmodiums
werd meer dan veertig jaar vertraagd door het feit
dat een eerste oriëntatie der opzoekingen steunde op de malaria
bij vogels.
Alhoewel men de verschillende cyclussen kende buiten de
rode bloedlichaampjes van de verscheidene menselijke parasieten
en van talrijke diersoorten, blijft in bepaalde gevallen nochtans
de oorsprong van de relapsus en de reden van de verlenging
der incubatieperiode bij Plasmodium vivax een vraagteken.
In t r o d u c t io n
* * *
I propose to describe the discovery of the third cycle of the
malaria parasites of primates including those of man, and to
discuss briefly the lacunae which remain. But first it is necessary
to mention the pointers which gradually indicated that such
a phase of development must exist.
It is a story af false clues. The first and most notorious
was the fallacious observation of Sc h a u d in n (1 9 0 3 ) that
the sporozoite made a direct entry into the erythrocyte; it was
therefore assumed to be unnecessary to consider the existence
of a tissue cycle. I shall indicate other misleading clues in the
course of this paper and you will see what a warning they
constitute to the research worker who can be led astray for
many years by retaining « preconceived ideas ».
Almost from the beginning of the modern history of malaria,
La v e r a n (1880) had realised that a second cycle must form
part of the life history of the malaria parasites which he had
demonstrated in the blood of soldiers in Algeria in 1880. The
second or mosquito cycle was elucidated in avian malaria seventeen
years later by Ross (1897) in India, while the Italians
(G rassi et al. 1898) confirmed transmission by anopheline
mosquitoes to man during the following year.
This seemed to be the end of the story until G rassi (1 9 0 0 )
suggested that the mosquito stage — the sporozoite — was