6

      Fresh specimens should be examined with the oil-immersion lens and with
carefully arranged light: if too much light passes through the specimens the
parasites are difficult to see.

      To those who are unfamiliar with malaria parasites the examination of
fresh specimens of blood is full of pitfalls. Anything which seems to have the
appearance of a parasite, but which is not actually inside a red blood corpuscle,
and especially such things as "free pigment," "free spores" (unless the
latter are actually seen breaking away from a segmenting parasite), should be
disregarded.

      In cases where there is any doubt and especially in cases where only
unpigmented forms appear to be present, it is better to take films and stain them
by Romanowsky's method.

      In stained films, unless scrupulous attention has been paid to the cleanliness
of the patient's finger, we should be on the watch for skin parasites, which often
present a superficial resemblance to malaria parasites.

      It is unnecessary, however, to enumerate all the things that may be mistaken
for malaria parasites, and experience has shown that no advantage is gained by
doing so:* it is sufficient to say that the malaria parasite is so definite an organ-
ism that anything about which, after careful examination, it is possible to have
the least doubt is almost certainly not a parasite.

      The detection of pigmented leucocytes.—It not infrequently happens in
cases of malarial fever, and especially in cases where the patient has been taking
quinine, that parasites are absent from the peripheral circulation. In such cases
it has been pointed out by Stephens and Christophers that the diagnostic value of
an examination for pigmented leucocytes and a differential count of the leucocytes
is very great.

      For both these examinations stained films should be employed. In an
examination for the detection of pigment in leucocytes, special attention should
be paid to the large mononuclear elements, for it is in these that the characteris-
tic appearances are chiefly found, The pigment may vary from a number of
large blocks or clumps to one or two fine spicules only, which may be difficult
to detect, but which, when recognised, are as absolutely diagnostic of recent
malarial infection as the presence of parasites. A common appearance is that of
one or two large blocks of pigment and a number of fine grains or spicules scat-
tered through the cell. Appearances as of pigment in any other elements

      * A great deal of very careful practice is necessary to become an adept at finding parasites, and I have
repeatedly seen men who could at once recognise a parasite when it was pointed out to them, spend an hour
or more over a film containing a fair number of parasites without being able to find one for themselves.
Even the Burman prisoners at Nagpur, who were well practised in examining slides, when examining
malignant Tertian cases, on several occasions passed over very obvious simple Tertian parasites which were
present in the films as well. On the other hand, it is even more common for men to think they see para-
sites in almost every field when none are present in the film at all.