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infected. The percentage of infected children affords, in fact, a very true test
of the endemicity of malaria in different places, and the figure representing
this percentage may, therefore, be termed the "Malarial Endemicity Index,"
or shortly the "Endemic Index."

      It would of course be possible to arrive at a rough estimate of the amount
of malaria and the liability to infection at different places by other methods
than this, as, for example, by an examination of the statistics of admissions into
hospitals for malarial fever, or by an estimation of the number of people with
enlarged spleens, but by neither of these methods can we arrive at an accurate
result, for neither of them will give us any information regarding the prevalence
of malarial parasites at the time of our examination. It is obvious that a
knowledge of the prevalence of parasites among the general population, and a
knowledge of the number of infected anopheles mosquitoes are the only reliable
data on which we can form an estimate of the amount of malaria and the danger of infection.

      The reasons for the great differences in the malarial endemicity of different
places in India shown in the above table will be discussed later: at present it is
necessary to refer to the significance of the infection of native children, and to
the relative immunity of the adult native.

      The great importance of the infection of native children lies in the fact
that they form undoubtedly the chief source from which anopheles mosquitoes
become infected. This is a point of the greatest practical importance and one
which cannot be too clearly recognised. That this must be so, is easily under-
stood when we remember that practically all the cases of malarial fever occurring
in native children are untreated, and go on for many months without it being
recognised by anyone that the children are suffering from malarial fever, and
have malaria parasites in their blood. A further proof is given in the fact that
the highest proportion of infected anopheles is found in the places where we
find the largest number of infected children; and in places where there are
no infected children it is difficult or impossible to find infected anopheles.
This is shown in the following table.