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

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the exoerythrocytic schizonts (Fig. 3) had a characteristic morphology
very different from those of P. vivax and P. cynomolgi.
R o d h a in had been watching this work with interest because
since 1940 he had been studying the behaviour of P. vivax
in the chimpanzee, and particularly the splenectomised chimpanzee.
As soon as we had reported our experiments on human
volunteers he realised the great possibilities which his ape model
offered for further research on the subject. He (R o d h a in 1953)
accordingly inoculated intravenously chimpanzees with large
numbers of sporozoites, did biopsies of the liver at various intervals
and watched the course of the infection in the (splenectomised)
animal. He was thus able to demonstrate the early
stages of development of the parasite in the parenchyma cells
of the liver at 4 days, to confirm the maturation time as
8 days, and to show the appearance of « relapse » bodies
9 months after the original infection. He found the relapse
schizonts in the liver entirely by accident: he was searching for
filaria in the sections when he suddenly discovered a beautiful
exoerythrocytic schizont and subsequently 3 others (R o d h a in
1956).
There is not time to describe in detail the novel techniques
which Colonel Sh o r t t and I introduced in these researches.
We realised from the start the importance of administering
really massive doses of viable sporozoites, for no multiplication
of the parasite occurs in the liver — one sporozoite growing
into a single schizont. If the number of sporozoites in the
inoculum were small, the search would resemble looking for
a « needle in a haystack ». Even a million sporozoites represent
but a fraction of the number of parenchyma cells in the human
liver; therefore a needle biopsy of the organ would be useless
and a piece of tissue at least 2 cm square is necessary, which
is obtainable only after laparotomy. Adequate staining of the
parasite in the sections is of course of paramount importance,
and the Giemsa Colophonium technique as modified first by
Sh o r t t and Co o per and later by B r a y and myself
( 1961), has proved to be ideal for its qualities of brilliance,
differentiation and permanence. W e eventually introduced mass
dissection of the salivary glands of infected mosquitoes and
by using 4 teams, we were able to dissect 250 mosquitoes in an