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examined in order to ascertain the percentage of children with enlarged
spleens.

       In the examination of the films the variety of parasite met with in each
slide should be noted, in order that the proportion of each variety present in the
village and district may be ascertained. The number of "large infections"
should also be noted, as if there are a good number of heavy infections there
will be more likelihood of finding infected anopheles.

       Having ascertained the endemic index, the next thing is to search
for adult anopheles in the houses, out-houses and stables, and to find out by
dissection—

(1) What species of anopheles are carrying malaria at the time.
(2) The percentage of infection with sporozoites of the malaria-carrying
   species.

       It will generally be found that only two or three species of anopheles are
present in sufficient numbers in the houses to be easily caught, and in order to
ascertain the two points noted above, at least one hundred anopheles of each
of these species should be dissected.

      It may happen that a fairly high percentage of infection (5—10 per cent.)
will be found in one species, and no infection at all in another, but before it can
be definitely stated that only one species of anopheles is carrying malaria in
any place, at least 300 or 400 of any other species than the one in which infection
was found should be examined.

     I have already described* the method of catching adult anopheles and
the best places in which to look for them, so it is unnecessary to do so here.
I may mention, however, that in places where anopheles are plentiful, a muslin
net will sometimes be found useful.

       We have proved that it makes no difference in the sporozoite rate whether
the anopheles in a village are caught in the stables and out-houses, or in the
houses where people are actually living, and sporozoites are as likely to be found
in mosquitoes caught in stables as in those caught in inhabited rooms. This is
a point of some importance, because it is far easier to catch anopheles in stables
and empty houses than in inhabited rooms.

       If desired, the anopheles which are caught may be kept in bottles until
they have got rid of their blood, and they may then be examined for zygotes,
but there is no particular object in determining the zygote rate as it gives
us little help in determining the liability to infection, for some at least of the
mosquitoes which are infected with zygotes will die before they reach the stage
when sporozoites are in the glands.

      * "The Causation and Prevention of Malarial Fevers; a statement of the results of researches, drawn
up for the use of Assistant Surgeons and Hospital Assistants," G. C. Press, Simla.

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