?( 19 )
Search for segmenting forms should be made an hour or so before the
time of onset of the febrile paroxysm. If one can secure a case of regularly
intermittent Quartan fever, very perfect segmenting " daisy like " forms will
be easily found in the peripheral blood.
The spirillum
obermeyeri.
The Filaria
nocturna.
Trypanoso
mata.
2.-The examination of specimens of blood for other parasites.
The possibility that other parasites than those of malaria may be present
in a blood film must always be kept in mind during the examination of the film,
and occasionally we should turn our attention away from the careful scrutiny
of the red blood corpuscles and concentrate it upon the clear spaces between
the corpuscles, focussing upwards and downwards with the fine adjustment
especially with a view to ascertain the presence or absence of the spirillar or
spirochete organism which is the cause of relapsing fever. (Plate II, g.) This
organism is about three times as long as a red blood corpuscle, but it is exceed
ingly thin and therefore is not easily detected in stained preparations unless the
observer's attention is concentrated upon the attempt. In the examination for this
parasite as well as for other parasites which occur free in the blood plasma, such
as trypanosomes and embryos of filariæ, it is best to employ in the first place
specimens of fresh blood. The fresh film to be examined for the spirochetes of
relapsing fever should be taken during a period of pyrexia and examined with
a one-sixth inch objective. The movements of the parasites cause a vibratory
disturbance of the corpuscles which plainly indicates that a living organism
is moving about amongst them. Afterwards dry films should be prepared
and stained and examined with the one-twelfth inch objective. The fresh
film to be examined for filarial embryos should be taken as late in the even-
ing as possible, because as a rule they appear in the peripheral blood at night-
time only. The examination should be made with a two-thirds inch objective
with which, owing to their comparatively large size, the embryos can be plainly
seen violently pushing the corpuscles about in all directions. (Plate II, d.)
Trypanosomes (Plate II, f) have not been found in human blood in India
up to the present but, they have been found in human blood in Africa where
they are the cause of the prolonged and fatal fever called trypanosomal fever
and of the deadly disease called sleeping sickness. They occur, however,
in many animals in India and one species, Trypanosoma lewisi, can be easily
studied in the blood of rats. Another species, Trypanosoma evansi, is the
cause of the fatal disease of horses, oxen, mules, camels, etc., named surra.
\ill\