NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
12
Figure 8 depicts a much enlarged parasite about to divide into two.
Many of these forms, however, instead of immediately dividing up, go on
enlarging. Their nuclei and blepharoplasts divide again, so that eventually
they may contain three or four nuclei and an equal number of blepharo-
plasts, figures 9, 10 and 11. Such a parasite on ceasing to enlarge splits up
into three or four smaller ones, figure 12, the protoplasm collecting around each
nucleus and blepharoplast. This process of multiple segmentation in the pre-
flagellate stage is uncommon, the parasites usually splitting into two before they
have attained any great size. This method of multiple segmentation in the
pre-flagellate stage is similar to that which takes place in the case of Herpeto
monas donovani in the human body. It will be seen then that the pre-
flagellate stage of Herpetomonas culicis is characterised by the growth of the
parasite, and its subsequent division, either by simple biniary fission or multiple
segmentation. This stage is found in the alimentary tract of the larva, but
may also be seen in the nymph, and even in the adult insect. As a rule, how-
ever, the parasite has flagellated when the larva becomes a nymph.
When the larvæ were removed from the water in which they became in-
fected, and were placed in clean water, which contained practically no food,
the development of the pre-flagellate stage was so retarded that when the larvæ
turned into nymphs, the parasites were still without flagella, and when the
adult insects hatched out of such nymphs, the parasites were still in their pre-
flagellate stage. Figure 29 depicts a young pre-flagellate as seen in an adult
mosquito, and figure 30 shows a pair of young flagellates from a mosquito. It
is clear then, that if the larvæ are unable to obtain sufficient food, the growth
and development of the parasites are so retarded, that they remain practically
unchanged throughout the larval stage and are then seen as pre-flagellates in the
mosquitoes which emerge later. This is a point worth noting, for it shews the
great precaution which must be observed when dealing with the life histories of
these parasites. It further emphasises the truth that the food of the insect has
a direct bearing on the life history of its herpetomonas. An observer who is
utilising a particular mosquito for feeding experiments on the blood of some
vertebrate, in order to see whether its blood parasite will develop in the
mosquito, would naturally collect a large number of larvæ, and place them in
jars or dishes in the laboratory. Now under these conditions, many of the
larvæ would certainly be starved, and if they contained a herpetomonas, its de-
velopment would be retarted, so that when the mature insects hatched out, they
would still contain the pre-flagellate stage of the parasite. After feeding such
mosquitoes, and on dissecting them, the observer would find the early stages, many
round forms and. young flagellates ; he might assume that these had originated
from the blood parasite which the insects had ingested. Such a conclusion
13
would obviously be erroneous, and would not only mislead the observer, but
also those who were not in a position to repeat his experiments.
The Flagellate Stage.
In my recent paper on the development of Herpetomonas donovani in the
bed bug, I advanced the view that the flagellum was of ectoplasmic origin, and
that it develops from a myoneme, which can nearly always be demonstrated in
stained preparations of the pre-flagellate stage. In support of this hypothesis
it was shewn that just prior to the extrusion of the flagellum, a pink staining
area appears in close proximity to the blepharoplast, and that the flagellum
may be seen to grow out directly from it. It was at first thought that this.
structure was of the nature of a vacuole, a view which was entirely based upon
its appearance in stained specimens ; but on studying a large number of this.
stage of herpetomonads, I came to the conclusion that the vacuole was in
reality a thickened myoneme, or rhizoplast of other authors, which had merely
become stretched and thus simulated a vacuole. I have drawn attention to the
presence of the flagellar myoneme in the pre-flagellate stage of H e r p e t o m o n a s
culicis, and it is depicted in figures 13 to 15 ; here however the characteristic
vacuole-like appearance is not usually seen, the myoneme appearing as a
thickened strand, which on further growth, results in the formation of the
flagellum, figure 16. I have been unable to trace any direct connection
between the flagellum and the blepharoplast.
Under normal food conditions, Herpetomonas culicis begins to flagellate in
the larval gut just prior to its becoming a nymph. One of two changes may
now take place ; (1) the parasites may either flagellate singly, or (2), they may
enlarge further, and then divide up into a rosette of four or more young
flagellates. I will first describe the changes undergone by the single flagellates.
As the flagellum is about to be extruded, it appears to be surrounded by a.
sheath, figures 18, 19 and 23; this in my opinion further supports the view that
the flagellum is in reality a part of the ectoplasm. At the same time the
nucleus and blepharoplast become enlarged prior to division. The flagellum
may now divide along its attached portion, and later split throughout its entire
extent. The parasite begins now to lose its globular appearance, its posterior
end growing out, resulting in the formation of a spindle shaped flagellate.
There are two views regarding the origin of the second flagellum, one that it is
an entirely new growth from the original flagellum, and the other that it is
formed by the splitting of the first flagellum. Whichever is the correct inter-
pretation, there can be no doubt that the second flagellum arises in close
proximity to the first one ; I am inclined to consider it to be the result of the
c2
14
division of, and the subsequent growth from, the parent flagellum. On the
division of the nuclei and blepharoplasts of these round or oval flagellates, they
split up longitudinally into two smaller forms, which later elongate and. produce
the typical flagellates. The second form of multiplication in the flagellate
stage is characterised by the formation of a number of round or oval flagellates.
A young parasite which is just flagellating enlarges, its nucleus and. blepharo-
plast dividing several times, the former passing towards the periphery, while the
latter is situated more centrally. As the flagella become extruded they are
directed towards a common centre, thus producing a typical rosette, figures 20,
21, 22 and 24. As these rosettes increase in size, the individual parasites
begin to split off, and the lines of cleavage are clearly seen passing down
between them, figure 21. The flagella now begin to grow out between the
parasites, and the anterior ends of each individual cell becomes clearly defined,
figure 22. Later the parasites break away, and then develop further as has
been described in the case of the single round or oval forms.
In the fresh condition these rosettes are extremely striking objects, for on
being freed from the intestinal contents, they may be seen whirling round like
the well known Catherine Wheels of pyrotechnical displays. They are usually
seen on the first and second day of the nymphal stage but may also be found in
the adult insect. Figure 24 depicts a rosette of twelve parasites from the mid-
gut of a mosquito. Many of the rosettes may be seen breaking up before the
individual parasites have elongated, and figures 27 and 28 depict several of
these forms. Their flagella are extremely active, in the fresh condition, and
their nuclei and blepharoplasts may be seen in all stages of division, figure 30.
These round or oval flagellates later enlarge, and become spindle shaped as
described above. It will be seen from this account of this stage of Herpeto-
monas culicis that it is exactly similar to the same stage of Herpetomonas
donovani in Cimex rotundatus, multiple segmentation however being better
marked in the mosquito herpetomonad.
As in the case of Herpetomonas donovani the typical mature flagellate
stage may be produced in one of two ways, either by the single round parasites,
which on flagellating, elongate, or they may be produced as a result of multiple
segmentation and further growth of the young flagellates.
The typical flagellate stage of Herpetomonas culicis is best seen in the
mosquito as it emerges from the nymph ; they will then be seen actively mov-
ing about in a greenish substance, the remains of the larval food, in the lower
part of the mid-gut of the insect. They may however be found all up the mid-gut,
even as far as the proventriculus. In the fresh condition they will be seen to
be actively dividing. This stage of the parasite measures from 15 μ t o 2 5
μ in
length and from 3 μ to 5 μ in breadth ; on staining them with Romanowsky's
15
stain, their structural details will be well seen, figures 31 to 38. The blepharo-
plast usually lies about 2. 5µ from the anterior end, which is always slightly
rounded ; the flagellum, which arises close to it, at once projects freely, and may
meas ur e f r om 25 µ t o 40 µ i n l engt h. I t cons i s t s of a deepl y s t ai ned f i l ament
which appears to lie in a close fitting sheath, the ectoplasm of the parasite.
The nucleus usually lies from 8 µ to 10 µ from the anterior end ; it is nearly
always oval in shape, measuring from 2 µ to 2.5 µ in length and from 1 µ to
1.5 µ in breadth. The protoplasm of the parasite stains a light pink and con-
tains a number of vacuoles, and large pink granules which are usually situated
towards the posterior end which is more or less pointed. These forms divide by
simple longitudinal fission. Just prior to division, the nucleus and bleph-
aroplast enlarge, and the flagellum begins to split at its basal end, a line of
division now begins to form, and on the separation of the nucleus and bleph-
aroplast into two, the parasite splits longitudinally. In the fresh condition
these flagellates exhibit extremely active movements, they dart across the field
of vision, the flagellum vibrating and drawing them along ; they are able to
turn with great rapidity.
Several experiments were carried out to see the effect of varying foods on
the flagellate stage of Herpetomonas culicis. Mosquitoes (C. fatigans) were bred.
out from larvæ taken from the septic tank, they were placed in small glass jars
and small pieces of banana were given them to feed on ; they were then dis-
sected and examined. in the fresh condition at varying intervals. Owing to the
fact that yeasts readily developed on the bananas, it was not found possible to
carry this experiment to its conclusion ; as soon as a mosquito became in-
fected with these yeasts, the flagellates disappeared and could not be found in
any part of the alimentary tract of the insect. In a few instances it was noted
that the adult flagellates soon left the upper part of the alimentary tract of the
mosquito, and passed down into the hind. gut and rectum, where they were be-
ginning to shew the earliest changes towards the formation of the post-flagellate
stage. This experiment recalls a very similar one with Herpetomonas muscæ
domesticæ in Musca nebulo. It will be remembered that it was found that
when infected flies were fed on jam, the post-flagellate stage of the parasite was
produced at an earlier stage than when the flies were fed on meat juice. This
experiment again points to the important bearing the food of an insect has on
the life processes of its herpetomonas.
In another experiment a number of recently hatched female mosquitoes
were allowed to feed. on human blood, and. they were dissected at varying in-
tervals. Although most of the controls were found to be heavily infected with
the flagellates, not a single one of those which had fed on blood, and been dis-
sected 24 hours later contained any flagellates. The experiment was repeated
16
and practically the same result was found, except that in a few of the insects
there were a considerable number of flagellates. It was noted that here again
the flagellates tended to pass on to their post-flagellate stage, but there could be
no doubt that human blood had some injurious effect on the flagellated forms of
Herpetomonas culicis. It was this experiment which led me to discover the
important fact that the flagellate stage of Herpetomonas donovani in Cimex
rotundatus is readily destroyed when brought in contact with fresh human
blood. I had hoped to have carried out a long series of experiments with H.
culicis in order to discover the true explanation of the phenomenon noted above,
but as this work would necessarily entail a long series of observations, it had to
be abandoned. I hope however to again return to the study of this important
problem, for I am convinced that the study of the action of human blood on
such a flagellate as Herpetomonas culicis will help us to understand the origin
of those forms which are now known to have passed from the insect to man ;
in short it will give us the clue as to how a harmless flagellate may evolve into
a pathogenic one.
The herpetomonads of mosquitoes throughout the first part of their life
histories, are accustomed to living in a medium, consisting chiefly of the animal
matter, found in water. In the case of the male mosquito the remaining part
of their life histories are spent in a medium consisting of plant juices. In the
female mosquito, on the other hand, they are suddenly brought in contact with
blood which must necessarily have a profound effect on their life processes.
The Post-flagellate stage.
This stage is characterised by the formation of the resting phase of the
parasite, which is destined to be passed on to another insect. It is best studied
in the male mosquito for it will live in captivity for a short time with little or
no food.
Text Fig. 2.
17
Text figure 2 depicts the alimentary tract of an infected male mosquito as
seen under a low power. The mid-gut contains the mature flagellates while the
hind gut is packed with layers of short oval bodies, the post-flagellate stage ;
scattered here and there are islands of the final encysted stage. This appearance
is very characteristic, and the intestine, when it is dissected out, has a stiff
appearance and it readily breaks. The flagellates may be seen actively moving
about in all parts of the hind gut and large numbers will be seen in the rectum
between the papillæ ; they are thus readily passed out by the mosquito in its
excreta. The figure was drawn from an actual preparation.
The early phase of the post-flagellate stage is characterised by the flagel-
lates collecting all along the hind gut. They fix themselves by their flagellar
ends to the intestinal wall, and on coming to rest, divide in such a regular man-
ner that a typical palisade, consisting of rows upon rows of spindle shaped
bodies, is produced. This regular formation then is the result of the division of
the flagellates. It should be remembered that it is not in every mosquito, that
the parasites are found in such enormous numbers as is depicted in the text
figure. In the majority, they will be found to only occupy that segment of the
hind gut just above the rectum, in others they will be seen collected high up ;
in a few they will be seen scattered about in small patches or islands. They
may therefore be readily overlooked. On staining such a preparation as that
depicted in the text figure all the various changes undergone by the parasites at
this time can be easily studied. Figure 39 shews a flagellate about to round up,
its posterior end is losing its rounded appearance, the protoplasm collecting
about the nucleus. The flagellum soon begins to have a shredded appearance,
and its basal part becomes indistinct, so that it appears to be lying loosely in its
sheath. In a still later stage it seems to be just attached to the margin of the
cell, figures 40 to 43. The nucleus and blepharoplast now divide, and the
parasite splits into two, and these in their turn divide again till the final
encysted form is reached, figures 34 to 47. The cysts are round or oval
bodies with a light pink staining protoplasm, and. granular nuclei, their ble-
pharoplasts are still rod shaped and usually lie well towards the centre of their
bodies. The ectoplasm consists of a pink staining rim, ensheathing the
parasite. These post-flagellates adhere together in masses, and they are then
passed out en masse.
Conclusions.
Herpetomonas culicis is a natural flagellate of Culex fatigans, passing its
complete life history in the larva, nymph, and imago ; it is in no way connected
with any vertebrate blood parasite. It, or any of its allied forms, should be
18
rigidly excluded in the case of experiments carried out with mosquitoes and the
parasites of Kala Azar, and Oriental Sore. These flagellates of mosquitoes
should be carefully studied, for as they are parasitic in insects which suck man's
blood their life histories may become so modified that they may in time be
transmitted to the human body and become pathogenic.
19
Explanation of Figures on Plate.
Figure 1.—An early pre-flagellate form, note the flagellar myoneme extending across the
body of the parasite.
Figure 2.—An enlarged pre-flagellate, the flagellar myoneme and the pink granules are well
seen.
Figure 3.—A much enlarged pre-flagellate, the blepharoplast is about to divide, the nucleus
is enlarged; the protoplasm contains many pink staining granules.
Figure 4.—An oval pre-flagellate, the blepharoplast is thickened, and the nucleus is just about
to divide.
Figure 5.—A pre-flagellate which has split into two.
Figure 6.—An enlarged pre-flagellate, the result of the further growth of the form depicted in
figure 4; the parasite does not yet shew any signs of splitting.
Figure 7.—A similar parasite, but here the posterior end shews the early appearance preced-
ing simple biniary fission.
Figure 8.—A much enlarged pre-flagellate about to divide, the blepharoplasts are already
thickened ready for the next division.
Figure 9.—A pre-flagellate shewing the early changes towards multiple segmentation.
Figure 10.—Another similar parasite, the nucleus and blepharoplast have divided once, and
one of the daughter nuclei and blepharoplasts have divided again.
Figure 11.—A still further stage of the same.
Figure 12.—Multiple segmentation in the pre-flagellate stage.
Figure 13.—The early changes towards flagellation, the flagellar myoneme is well marked.
Figure 14.—A further stage of the same, there is just the faintest suspicion of the vacuole-
like appearance.
Figure 15.—A very similar parasite, the vacuole-like area is better marked and the myoneme
is considerably thickened.
Figure 16.—A similar parasite, the nucleus is much enlarged and the blepharoplast is
thickened.
Figure 17.—A young flagellate, the flagellum is just protrading freely, the blepharoplast is
about to divide.
Figure 18.—Another young flagellate, note the flagellum has the sheath well seen at its base,
the nucleus is about to divide.
Figure 19.—A young flagellate with well developed flagellum, which is splitting at its base.
Figure 20.—A rosette of four parasites, shewing multiple segmentation in the flagellate stage.
Figure 21.—A typical rosette, note the position of the nuclei and blepharoplasts ; the flagella
are all passing out at one point and the anterior ends of the parasites are not
clearly defined.
Figure 22.—A well developed rosette, the parasites are now quite separate, the flagella have
grown out between each parasite.
Figure 23.—A young oval flagellate, the flagellum has divided throughout its extent,
it is surrounded by a sheath.
Figure 24.—Another rosette.
Figure 25.—A spindle shaped flagellate with well developed flagellum. D
20
Figure 26.—A. round flagellate, separated from a rosette.
Figure 27.—A group of four round flagellates, shewing evidences of further division.
Figure 28.—Another group of four round flagellates, with flagella all passing out in one
direction.
Figure 29.—An early pre-flagellate from the mid-gut of a mosquito, note the absence of
granules.
Figure 30.—Two young flagellates from the mid-gut of a mosquito, both are dividing. It is
these forms, in the adult insect, which may lead to confusion.
Figure 31.—The mature flagellate stage of Herpetomonas culicis with a very long and stout
flagellum.
Figure 32.—Longitudinal division in the flagellate stage, the parasites only being attached
by their posterior ends.
Figure 33.—Another typical mature flagellate.
Figure 34.—A very long flagellate.
Figure 35.—A long flagellate showing the early phase of longitudinal division.
Figure 36.—A similar flagellate.
Figure 37.—A short flagellate dividing.
Figure 38.—Another similar flagellate.
Figure 39.—The early post-flagellate stage, the parasite is becoming globular.
Figure 40.—Another early post-flagellate, the blepharoplast is thickened and the flagellum is
seen to be attached to the margin of the body of the parasite, the basal portion
is faintly seen.
Figure 41.—Another post-flagellate, the nucleus and blepharoplast are about to divide.
Figure 42.—Another similar form.
Figure 43.—A more advanced post-flagellate, the flagellum is broken off and has a shredded
appearance ; the ectoplasmic layer is growing round the parasite.
Figure 44.—A post-flagellate dividing.
Figures 45, 46, and 47.—The final post-flagellate stage.
21
Reference to Literature.
Patton, W. S. (l907).—The life cycle of a species of Crithidia parasitic in the intestinal tract
of Gerris fossarum, Fabr. Archiv. fur Protistenkunde, Vol. XII, pp. 131—146.
Patton, W. S. (1908).—Herpetomonas lygœi. Archiv. fur Protistenkunde, Vol. XIII, Bd. I ;
PP. 1—18.
Patton, W. S. (1909).—The life cycle of a species of Crithidia parasitic in the intestinal tracts
of Tabanus hilaris and Tabauus sp ? Archiv, fur Protistenkunde, Vol. 15, pp.
333—362.
Patton, W. S. (1910).—Experimental infection of the Madras fly Musca nebulo, Fabr. with
Herpetomonas museœ domesticœ (Burnett) Bull. Soc. Path, Exotiq., Vol. III,
No. 4, pp. 264—273.
Ross, R. (1906).—Notes on the parasites of mosquitoes found in India, etc. Jour. Hygiene, Vol
VI, p. 101.
Durham, H. E. (1902).—Report of the Yellow Fever Expedition to Para. (1900). Thompson
Yates laboratories Report, Vol. IV, part 2, p. 563.
Chatterjee, B. C. (1901).—Parasites in Anopheles. Ind. Med. Gaz. Vol. 36, p. 371.
Léger, L. (1902).—Sur un flagelle parasite del' Anopheles maculipennis. Compt. rend. de la
Soc. de Biol. Vol. 51, pp. 354—356.
Léger, Land Duboseq,
O. (1902).—Sur les larves d' Anopheles et leur parasites en Corse.
Compt rend. de l' Assoc., franc. l' avanc. des Sciences, p. 703.
Sergent, Ed. and Et. (1906).—Sur un flagelle nouveau del'intestin des Culex et Stegomyia
Herpetomonas algericase: Sur un autre flagelle et sur des spirochætes,
del'intestine des larves de moustiques. Compt. rend. de la Soc. de Biol. Vol.
60, pp. 291—293.
Adie, J. R. (1907).—A plea for scraps. Ind. Med. Gaz. Vol. 42, No. 7.
Wenyon, C. M. (1911).—Oriental Sore in Bagdad, together with observations on a Gregarine
in Stegomyia fasciala the Hœmogregarines of dogs and the Flagellates of House
Flies Parasitology. Vol. 4, No. 3.
Franchini, G. (1911).—Note on Leishmania and Mosquitoes. The Lancet, Vol. 2, pp. 1268
—
1269.
Franchini, G. (1912).—On the presence of Leishmania in the digestive tract of Anopheles
maculipennis. Ann. Trop. Med. and Parasit. Vol 6, No. 1, pp. 41—48.
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