Chapter VII: Appendix: “Rhizopods in Poliomyelitis acuta.” (1)

In three cases of poliomyelitis acuta which were investigated
by Ellermann, the spinal fluid obtained by puncture of the cord
contained bodies, from 10 µ to 15 µ in size, which had amœboid
movements and exhibited variously shaped pseudopodia in large
numbers. After staining, a usually excentric nucleus, about 1·5 µ in
size, was demonstrated in them.

Order. *Foraminifera*, d’Orbigny.

The order is divided by Max Schultze into Monothalamia and
Polythalamia. Only a few of the former can be considered here.

Sub-Order. *Monothalamia.* (Testaceous Amœbæ).

These forms occur frequently in fresh water, rarely in sea water. They possess a shell which is either pseudo-chitinous in character, or consists of foreign particles, or in a few cases is composed of siliceous lamellæ. There is usually an orifice for the protrusion of pseudopodia. The only representative of the order of interest here is:--

Genus. *Chlamydophrys*, Cienkowski, 1876.

The genus is based on a form which A. Schneider carefully
investigated and considered to be the _Difflugia enchelys_ of
Ehrenberg. L. Cienkowski rediscovered this same form and created
for it the genus _Chlamydophrys_. We agree with this view, but not
with the renaming of the organism (so common at the time). If the
parasite in dung, _Chlamydophrys stercorea_ Cienk. is identical with
_Difflugia enchelys_ of Ehrenberg, the old specific name should be
retained.

The genus is characterized by the possession of a hyaline, structureless, slightly flexible shell which is ovoid or reniform. At the more pointed pole there is an orifice situated terminally or somewhat laterally, serving for the emergence of the filiform pseudopodia (fig. 13, _a_). The protoplasm does not entirely fill the interior of the shell. An equatorial zone bearing excretory granules divides the shell internally into two almost equal portions. The anterior portion is rich in vacuoles and serves for the reception of nutriment and for digestion. The posterior part is vitreous, and contains the nucleus. One to three contractile vacuoles are situated in the equatorial zone.

*Chlamydophrys enchelys*, Ehrbg.

Syn.: _Chlamydophrys stercorea_, L. Cienkowski.

This species (fig. 13) is found in the fæces of various animals (cattle, rabbits, mice, and lizards), and also in quite fresh human fæces. According to Schaudinn, the parasite occurs so frequently in the human fæces that it must be considered of wide distribution. The species must traverse the intestine of man and animals during one stage of its life cycle, as Schaudinn showed by experiments on himself and on mice. He infected himself with cysts (fig. 14) by swallowing them, and evacuated the first _Chlamydophrys_ as early as the following day. After the evacuation of numerous specimens on one of the following days the infection ceased.

The nucleus of a living specimen is surrounded by a hyaline, strongly refractile chromidial mass, arranged in the form of a ring. Chromatin stains colour it darkly.

_Asexual multiplication_ (fig. 13, _b_), which takes place in fæces, follows a similar course to that of allied forms (_e.g._, _Euglypha_, _Centropyxis_). It commences by the cytoplasm issuing from the orifice of the shell and assuming the shape characteristic of the mother organism, but in a reverse position. The nucleus then divides by mitosis, when the daughter nuclei move apart from one another. The chromidial ring also divides into two portions by a process of dumb-bell like constriction. The one daughter nucleus remains in the mother organism, the other moves towards the daughter individual, which then separates from the parent.

In this species plasmogamic union of two or more individuals (up
to twenty) is frequently observed. Such colonies may similarly
divide, and in this way monstrosities frequently arise. When drying
of the fæces, or deficiency of food occurs, encystment takes place
apparently spontaneously. The whole body, as stated by Cienkowski,
issues from the shell, assumes a spherical shape (probably with
discharge of water) and becomes surrounded with a thick membrane
(fig. 14). After the addition of water and the escape of the encysted
_Chlamydophrys_, a new shell must be formed. Schaudinn, who has not
given a more detailed description of the process of encystment in
this species, but refers to Cienkowski and to similar observations
made on _Centropyxis_, states of the latter that the encystment takes
place within the shell.

The _sexual multiplication_ is accompanied by shedding of all the foreign bodies and of the degenerating nucleus. The protoplasm, now contracting into a sphere, remains behind in the shell with the chromidial mass. From the latter several new nuclei arise (sexual nuclei) often eight in number. The cytoplasmic sphere then segregates into as many spherical portions as there are nuclei present. When they have assumed an oval form, two flagella develop at one pole and the flagellispores swarm out of the shell.[35] The biflagellate swarm-spores, or gametes, copulate in pairs and apparently the individuals of the pairs of gametes arise from different mother organisms. The zygote secretes a thick covering which soon becomes brown and rough. These zygote cysts or resistant spores must now pass from the intestine of an animal in order to complete their development. The escape of the cyst contents does not always take place in the intestine; often it does not occur until after defæcation. These shell-less individuals (amœbulæ) soon become invested with a shell. But in the alkaline intestinal contents, shell formation may proceed even while the organism is in the intestine, and multiplication may take place.

[35] Schaudinn (1903), _Arb. a. d. Kaiserl. Gesundh._, xix, p. 547.

Schaudinn’s further communication was of special interest; it was to the effect that _Chlamydophrys_ was related to

*Leydenia gemmipara*, Schaudinn, 1896.

In the fluid removed by puncture from two patients suffering from ascites in the first medical clinic in Berlin, cellular bodies with spontaneous movement were found, which Leyden and Schaudinn regard as distinct organisms. They remained alive without the use of the warm stage for four or five hours, the external temperature being 24° to 25° C. In a quiescent condition they were of a spherical or irregular polygonal form. Their surface was rarely smooth, being beset with protuberances and excrescences (fig. 15). The substance of the body was thickly permeated with light refractile granules with a yellowish shimmer. The hyaline ectoplasm was rarely seen distinctly. All sizes from 3 µ to 36 µ in diameter were observed. The movements were rather sluggish, the ectoplasm in the meantime appearing in the form of one or several lamellæ, in which also strings of the granular endoplasm occurred, and frequently protruded over the border of the hyaline pseudopodia. The tendency for the joining of several individuals by means of their pseudopodia was so marked that associations ensued similar to those known in free-living Rhizopoda.

The cytoplasm enclosed blood corpuscles as well as numerous vacuoles, one of which pulsated slowly about every quarter of an hour. A vesicular nucleus the diameter of which was about equal to one-fifth of the body was present.

Multiplication took place by means of division and budding (fig. 15, _c_), after previous direct division of the nucleus. The buds were supposed to divide repeatedly soon after their appearance, thus giving rise to minute forms of 3 µ.

There was a suspicion in both cases that the ascites was associated with malignant neoplasms in the abdomen, and autopsy confirmed this view in one case.

The parasite, which has seldom been observed, has been variously interpreted; for example, it has been regarded merely as altered tissue cells. It is now known, from Schaudinn’s researches, that _Leydenia gemmipara_ is connected with abnormal conditions of _Chlamydophrys_, occasionally occurring as a commensal in the ascitic fluid. The form is produced when pathological conditions of the large intestine create an alkaline reaction of its whole contents. The formation of shells then often ceases, and these naked _Chlamydophrys_ are enabled to multiply atypically by division and gemmation. Such stages, which are no longer capable of a normal development, are the _Leydenia_, as Schaudinn has demonstrated.

Class II. *MASTIGOPHORA*, Diesing.

Sub-Class. FLAGELLATA, Cohn emend. Bütschli.

During the motile part of their life the Flagellata possess one
or more flagella which serve for locomotion, and in many cases
also for the capture of food. A few groups (_Euglenoidinæ_,
_Choanoflagellata_) have only one flagellum, others two or several
of about equal length (_Isomastigoda_), or of various lengths
(_Monadina_, _Heteromastigoda_, _Dinoflagellata_). The long flagellum
is the principal one; the smaller ones on the same organism are
accessory flagella. The flagella directed backwards, which occur in
the Heteromastigoda and are used for clinging, are termed trailing
flagella or tractella. At the base of the flagellum, which is
almost always at the anterior end, a Choanoflagellate possesses a
cytoplasmic funnel-shaped neck or collar. In the parasitic forms an
undulating membrane is often present.

The body of the Flagellata is usually small, generally elongate and
of unchangeable form. It is frequently covered by a distinct cuticle,
and, in certain groups, by a hard envelope, or it may be more or
less loosely enveloped by a gelatinous or membranous covering. An
ectoplasmic layer is thin and not always obvious. The granular
cytoplasm contains a varying number of vacuoles, one of which may be
contractile, and is generally situated near the area from which the
flagella arise, that is, at the anterior extremity. The cytoplasm,
moreover, contains the nucleus, which is nearly always single; and in
many species there are also yellow, brown, or green chromatophores
of various shapes, such as occur in plants. Some species feed after
the manner of green plants (holophytic), or of plants devoid of
chlorophyll (saprophytic); others, again, ingest solid food, and
for this purpose usually possess a cytostome; the latter, however,
in a few forms is not used for its original function, but is
connected with the contractile vacuole. Many parasitic forms feed
by endosmosis. A few species possess eye-spots with or without
light-refracting bodies.

Variation in the form of the nuclear apparatus occurs. One nucleus
only, which may be compact or vesicular, is known in many species.
This nucleus is situated either centrally or sometimes near the
flagellar end of the body, but its position is subject to variation.
The flagella may arise near the nucleus. Other structures, such as
an axial filament and a rhizoplast, may be present. Some flagellates
are binucleate, the two nuclei--which often differ in size and
shape--being separated from each other. One of these nuclei is the
principal, vegetative or trophic nucleus; the other is an accessory
nucleus, frequently termed the blepharoplast, flagellar or kinetic
nucleus. One or more small basal granules are often present at or
very near the origin of the flagella.

Multiplication is by fission, usually longitudinal, which may occur
in either the free or encysted forms. Division is initiated by that
of the nucleus or nuclei (especially the kinetic nucleus). The
basal granule divides also. Collars and chromatophores, if present,
likewise separate into two. Variation in the method of doubling the
original number of flagella occurs. In most organisms, especially
uniflagellate forms, the flagellum splits lengthwise, after division
of the basal granule, blepharoplast and nucleus. The daughter
flagella may be of the same or different lengths and thicknesses.
Other flagellates at division are said to produce new flagella in the
neighbourhood of the original ones. The daughter organisms in such
cases are provided with one or more parental flagella in addition
to newly formed ones. It has been stated that in certain cases the
parent flagellate retains all its flagella, while new ones arise _ab
initio_ in the cytoplasm of the daughter forms.

Multiplication by longitudinal fission may be interrupted sooner or
later by the production of gametes, which form zygotes, from which
new generations of individuals arise. In many flagellates gamete
formation and sporogony are unknown, and asexual reproduction by
fission alone prevails.

Incomplete division results in the formation of colonies of
individuals. These colonies must not be confused with the aggregation
rosettes of flagellates found among the parasitic Mastigophora.
The individuals of aggregation rosettes are capable of immediate
separation from the rosette at will.

A number of parasitic Flagellata produce non-flagellate stages which
are very resistant to external conditions, the assumption of which
forms serves to protect the organisms during their transference
from one host to another. Such non-flagellate forms possess one
or more nuclei, are usually of an oval or rounded contour, and
are capable of developing into the full flagellate on the return
of more favourable conditions. These forms are often known as the
post-flagellate stage of the organism. When ingested by a new host,
the post-flagellate coat becomes more flexible, and the phase of the
organism which now recommences growth is known as the pre-flagellate
stage; it gradually develops into the typical flagellate organism.

Many Flagellata live free in fresh and salt water. They prefer
stagnant water, rich in organic products of decomposition, such as
puddles, swamps and pools. Those forms developing shells and colonies
are, as a rule, adherent. A number of species are parasitic in man
and animals, living mostly within the intestine or in the blood.

It is usual to classify the Flagellata in four orders:
_Euflagellata_, _Dinoflagellata_, _Choanoflagellata_, and
_Cystoflagellata_, of which only the _Euflagellata_ are of interest
to us. This is a group comprising numerous species, for the further
classification of which the number and position of the flagella are
utilised.

The Euflagellata observed in man belong to the Protomonadina as well
as to the Polymastigina. The former possess either only one or two
similar flagella, or one principal and one or two accessory flagella.
The Polymastigina possess at least three flagella of equal size,
or four to eight of unequal size, inserted at different points. An
undulating membrane may be present in members of both groups.

It must also be pointed out that unicellular organisms with one or
several flagella are not always classified with flagellates, for such
forms occur in Rhizopods as well as temporarily in the lower plants.
In addition, the examination of the flagellates, especially the
parasitic species, is very difficult on account of their diminutive
size and great activity; thus it happens that certain forms cannot
with certainty be included in the group because their description is
insufficient.

Order. *Polymastigina*, Blochmann.

The Polymastigina contains flagellates with three to eight flagella. Some of the Flagellata parasitic in man belong to the Polymastigina, and to two or three genera that are easily distinguishable.

Genus. *Trichomonas*, Donné, 1837.

The body is generally pyriform, the anterior part usually rounded,
the posterior part pointed. There are at the anterior extremity three
(? four) equally long flagella that are sometimes matted together.
A blepharoplast (kinetic nucleus) and basal granule are present,
together with a supporting structure known as an axial filament or
axostyle. In addition there is an undulating membrane, bordered by
a trailing flagellum, that commences at the anterior extremity and
proceeds obliquely backwards. The nucleus, which is vesicular, is
situated near the anterior extremity, and behind it are one or more
vacuoles, none of which seems to be contractile. These flagellates
are parasitic in vertebrate animals, and live chiefly in the
intestine.

*Trichomonas vaginalis*, Donné.

The form of the body is very variable, and is elongate, fusiform or pear-shaped, also amœboid. The length varies between 15 µ and 25 µ, and the breadth between 7 µ and 12 µ. The posterior extremity is drawn out to a point and is about half the length of the remainder of the body. The cuticle is very thin and the body substance finely granular. At the anterior extremity there are three--some say four[36]--flagella of equal length which are frequently united together, at least at the base, and are easily detached.

[36] To explain this discrepancy it is stated that the border of the undulating membrane can be detached in the form of an independent flagellum. But Parisi (1910) places such quadriflagellate forms in the sub-genus _Tetratrichomonas_, _Arch. f. Protistenk._, xix, p. 232.

There is an undulating membrane (fig. 16) which runs spirally across the body, arising from the place of insertion of the flagella, and terminating at the base of the caudal process. A cytostome seldom is recognizable in fresh specimens, but is apparently present. The nucleus is vesicular, elliptical and situated near the anterior extremity.[37]

[37] According to Marchand, the nucleus is connected with a line, which becomes visible on addition of acetic acid, terminates at the posterior extremity, and does not correspond to the line of insertion of the undulating membrane. This formation probably is the same as the axostyle in _Trichomonas batrachorum_, Perty. Blochmann (1884) also mentions two longitudinal rows of granules, which commence at the same place as the nucleus and converge posteriorly.

Multiplication takes place by division (Marchand). Encysted forms are almost unknown.

_Trichomonas vaginalis_ lives in the vaginal mucus of women of
various ages, not in normal mucus, but in mucus of acid reaction.
It is found in menstruating females as well as in females who
have passed the menopause. It occurs in pregnant and non-pregnant
women, even in very young girls, provided always that they have a
vaginal catarrh with acid reaction of the secretion. Should the acid
reaction change, as, for instance, during menstruation, the parasites
disappear, as they do likewise on injection of any alkaline fluid
into the vagina. A low temperature (below +15° C.) is also fatal to
the parasites. These flagellates can pass from the vagina through the
urethra into the bladder, and produce severe catarrh, and are not
easily removed.

_T. vaginalis_ appeared to be a parasite specific to the female organs and not transmissible to man. However, several observations have since been made that confirm the occurrence of this species in the urethra of the male. The infection apparently takes place through coitus when changes are present in the urethral mucous membrane. At any rate, three cases observed point to this circumstance.

Attempts at experimental transmission to rabbits, guinea-pigs and dogs failed (Blochmann, Dock). So far, the manner in which women become infected is unknown.

*Trichomonas intestinalis*, R. Leuckart, 1879 = *Trichomonas hominis*, Davaine, 1854.

Some authors believe that a second trichomonad inhabiting man, _Trichomonas intestinalis_, R. Lkt., is identical with _Trichomonas vaginalis_, Donné. Leuckart’s species was based on the discoveries of Marchand (1875) and Zunker (1878), who stated that according to all appearances, and in their opinion, it was the same as _Cercomonas intestinalis_, Lambl, 1875 (_nec_ 1859), which they found in the fæces of patients suffering from intestinal disorders. The organism is described by them as being pear-shaped and 10 µ to 15 µ in length and 3 µ to 4 µ in breadth. The posterior extremity terminated in a point (fig. 17).

A row of twelve or more cilia was said to commence at the anterior
end and extend over the body. Leuckart stated that this parasite,
placed by the two authors in the genus _Cercomonas_, was a
_Trichomonas_, and that they mistook the undulating membrane for
cilia, and overlooked the flagella. Notwithstanding its striking
similarity with _T. vaginalis_, it was said to be distinguishable
from that species by differences in the undulating membrane. Lambl’s
_C. intestinalis_[38] (of 1875) which corresponds with _C. hominis_,
Davaine[39] (1854), is regarded by Leuckart as a true Cercomonad
(characterized by a flagellum and the absence of an undulating
membrane, see p. 61), and is thus generically distinct from
_Trichomonas_.

[38] Under the term _Cercomonas intestinalis_, Lambl in different years has described two entirely distinct Flagellata, namely, in 1859 (“Mikr. Unters. d. Darm- Excrete,” _Prag. Vierteljahrsschr. f. prakt. Hlkde._, lxi, p. 51; and Lambl, _A. d. Franz-Josephs-Kinderspitale in Prag_, Prag, 1860, i, p. 360), a form that at the present day is termed _Lamblia intestinalis_; and in 1875 (in the _Russian Medical Report_, No. 33), a species identical with _Cercomonas hominis_, Dav.

[39] Davaine, C., “Sur les anim. infus. trouv. dans les selles d. malad. atteints du cholera et d’autr. malad.,” _C. R. Soc. Biol._, 1854, ii, p. 129.

The correctness of Leuckart’s judgment in regard to Marchand-Zunker’s
flagellate was demonstrated by Grassi’s researches, accounts of which
were published soon after. In about 100 cases of bowel complaints
in North Italy and Sicily, Grassi found Flagellata in the stools,
which he first named _Monocercomonas_ and _Cimænomonas_, but later
termed _Trichomonas_. However, in opposition to Leuckart, Grassi
has also classified Davaine’s _C. hominis_ (= _C. intestinalis_,
Lambl, 1875) as _Trichomonas_, and most authors have followed his
example. Hence arose the use of the name _Trichomonas hominis_. It
was through Janowski (1896) that the former view was again taken
up. After a review of the literature, the occurrence of Cercomonads
in the intestine of human beings in addition to Trichomonads was
considered by the author to have been proved, and he added a
description of the Trichomonads. According to this, all morphological
distinction between _T. vaginalis_, Donné, and _T. intestinalis_,
Leuckart, disappeared. On the other hand, it is worthy of note
that the smaller size, the more pear-shaped form, and the longer
flagella differentiate _T. intestinalis_ (= _T. hominis_) from _T.
vaginalis_.[40]

[40] For the present the following should be regarded as synonymous: _Protoryxomyces coprinarius_, Cunningham (_Quart. Journ. Micr. Sci._ (2) 1880, xxi, p. 234), (_Zeitschr. f. Biol._, 1882, viii, p. 251). _Monocercomonas hominis_, Grassi, 1882. _Cimænomonas hominis_, Grassi, 1882. _Trichomonas hominis_, Grassi, 1888. _Cercomonas coli hominis_, May (_Deutsches Archiv. f. klin. med._, 1891, xlix, p. 51). _Monocercomonas hominis_, Epstein (_Prag. med. Wochenschr._ 1893, Nos. 38–40). _Trichomonas confusa_, Stiles (_Zool. Anz._, 1902, xxv, p. 689). _Trichomonas elongata_, _Trichomonas elliptica_, Cohnheim (_Deutsche med. Wochenschr._, 1903, xxix, Nos. 12–14). _Trichomonas elongata_, _Trichomonas caudata_, _Trichomonas flagellata_, Steinberg (_Kiewer Zeitschr. f. neuere Medicin_, 1862). _Trichomonas pulmonalis_, A. Schmidt, (_Münch. med. Wochenschr._, 1895, No. 51), and St. Artault (_Arch. de parasit._ 1898, i, p. 279).

The easily deformed pear-shaped body has three free flagella anteriorly, and an undulating membrane with its flagellar border terminating in a short free flagellum posteriorly (figs. 17, 18). The undulating membrane may coil itself spirally round the body. A supporting rod or axostyle projects as a posterior spine. It appears to begin near the nucleus and blepharoplast, which are situated near the more rounded, anterior end of the body. There may be a chromatoid basal supporting line along the body for the undulating membrane. Rows of chromatoid granules are sometimes situated along one side of the axostyle. A cytostome may sometimes be seen. In mice, Wenyon (1907) found these parasites to vary in length from 3 µ to 20 µ. They occur in the cæcum and intestine of mice, where their internal structure seems more obvious than in man. The flagellates divide by longitudinal fission.

_T. intestinalis_, R. Leuckart, appears to be capable of settling in all parts of the human intestine in which the contents have an alkaline reaction. Trichomonads have been cited as occurring in the oral cavity by Steinberg, Zunker, Rappin and Prowazek; in the œsophagus by Cohnheim, and in the stomach by Strube, Cohnheim, Zabel, Hensen and Rosenfeld. The normal situation seems to be the small intestine. The parasites then appear in the dejecta, especially in various intestinal diseases the course of which is connected with an increased peristalsis. They are also found in healthy persons, from whom they are obtained after the administration of laxatives. They have been regarded by some workers as commensals, which, however, have the power of accelerating the onset of intestinal complaints, or at least of adding to them. They have been found in cases of carcinoma of the stomach, and in other diseases of that organ in which the acid reaction ceased.

Naturally, whether all the reports relate to the same species of
Trichomonas must remain undecided. Certain authors (Steinberg,
Cohnheim, van Emden) accept several species. Prowazek speaks of a
variety of _T. intestinalis_ inhabiting the oral cavity. This was
distinguished by a posterior process exceeding the length of the
body fourfold, and by a somewhat unusual course of the undulating
membrane. The food of this form, which was found in the whitish
deposit present, especially in the cavities of carious teeth,
consisted almost exclusively of micrococci. Schmidt and St. Artault
named the Trichomonads found in pathological products (_e.g._,
gangrene, putrid bronchitis, phthisis) of the lungs of man, as
_Trichomonas pulmonalis_. Trichomonads have also been found by
Wieting in lobular pneumonia in the lungs of pigs.

It is still uncertain in what way the infection takes place.
Experiments in the transmission of free trichomonads to mammals (_per
os_), in which the same or allied species occur (guinea-pigs, rats,
apes), have been without result. Probably encystment is necessary.
Such conditions are mentioned by May, Künstler, Roos, Schurmayer, van
Emden, Prowazek, Galli-Valerio and Schaudinn. According to Prowazek,
intestinal trichomonads of rats become encysted for conjugation. In
the cyst an accumulation of reserve food material occurs, causing
distension. The nuclei of the conjugants each give off a reduction
body and, after fusion, produce the nuclei for the daughter
individuals. According to Schaudinn the intestinal trichomonads lose
their flagella before conjugation, become amœboid and encyst in
twos, the formation of a large agglomeration of reserve substance
accompanying this. Galli-Valerio found double-contoured cysts in
the fæces of trichomonad-infected guinea-pigs, after the fæces had
been kept for a month in a damp chamber. When exposed to heat small
flagellates escaped from them. Administration of such material
containing cysts resulted in severe infection with trichomonads,
and death of the experimental guinea-pigs followed. The cyst wall
is clearly a protection against the deleterious acid reaction of
the stomach contents. Alexeieff (1911) and Brumpt (1912) think that
the trichomonad cysts of man are really fungi, while other workers
also doubt encystment among trichomonads. Wenyon (1907) states that
_T. intestinalis_ in mice produces spherical contracted forms which
escape from the body in the fæces.

Air, water, and under certain circumstances even food may be regarded
as vectors for the trichomonads. The occurrence of the organisms in
the oral cavity, and still more so in the lungs, is in favour of the
air being the transmitting agent. An observation made by Epstein
supports the idea of water transmission. Multiplication of the
trichomonads, once they have gained access to the body, is effected
by longitudinal division commencing at the anterior end (Künstler).
“Cercomonads” with several flagella and an undulating membrane, as
well as trichomonads, have been observed by Ross in some cases of
cutaneous ulcers.

Mello-Leitao (1913)[41] has described flagellate dysentery in children in Rio de Janeiro. He states that it is due to _T. intestinalis_ and _Lamblia intestinalis_ either separately or together. Flagellate dysentery, he thinks, is benign and is the most frequent form of dysentery in infants. The flagellates are pathogenic to infants under three years of age. Escomel (1913)[42] found 152 cases of dysentery in Peru due solely to Trichomonas. Such cases are probably widespread.

[41] _Brit. Journ. Children’s Diseases_, x, p. 60.

[42] _Bull. Soc. Path. Exot._, vi, p. 120.

Genus. *Tetramitus*, Perty, 1852.

*Tetramitus mesnili*, Wenyon, 1910.

Syn.: _Macrostoma mesnili_, _Chilomastix mesnili_, _Fanapapea
intestinalis_.

The genus _Tetramitus_ differs from _Trichomonas_ in possessing an undulating membrane inserted in a deep groove or cytostome. There are three anterior flagella. The pear-shaped organism measures 14 µ by 7 µ, but smaller examples occur. _T. mesnili_ occurs in the human intestine, having been described by Wenyon[43] (1910) from a man from the Bahamas in the Seamen’s Hospital, London. Its occurrence is widespread. Alexeieff considers that _Macrostoma_ and _Tetramitus_ are synonymous. The parasite is the same as _Fanapapea intestinalis_, Prowazek, 1911, from Samoa. Brumpt (1912) found _T. mesnili_ to be the causal agent of colitis in a Frenchwoman. Nattan-Larrier (1912) considers it of little pathological importance.

[43] _Parasitology_, iii, p. 210.

Gäbel[44] (1914) described an interesting case of seasonal diarrhœa acquired in Tunis, in which a new Tetramitid was the causal agent. The organism was pear-shaped, without an undulating membrane, and measured 6·5 µ to 8 µ by 5 µ to 6 µ. The cytostome was large, and there was no skeletal support. Encystment occurred. Gäbel named the organism _Difämus tunensis_ and considered that it was pathogenic.

[44] _Arch. f. Protistenk._, xxxiv, p. 1.

Genus. *Lamblia*, R. Blanchard, 1888.

Syn., _Dimorphus_, Grassi, 1879, _nec_ Haller, 1878; _Megastoma_,
Grassi, 1881, _nec_ de Blainville.

The body is pear-shaped, with a hollow on the under surface
anteriorly. It has four pairs of flagella directed backwards, of
which three pairs lie on the borders of the hollow disc, and the
fourth arises from the pointed posterior extremity.

*Lamblia intestinalis*, Lambl, 1859.

Syn.: _Cercomonas intestinalis_, Lambl, 1859 (_nec_ 1875); _Hexamitus
duodenalis_, Davaine, 1875; _Dimorphus muris_, Grassi, 1879;
_Megastoma entericum_, Grassi, 1881; _Megastoma intestinale_, R.
Blanch., 1886; _Lamblia duodenalis_, Stiles, 1902.

The organism is pear-shaped and bilaterally symmetrical. It is from 10 µ to 21 µ long and 5 µ to 12 µ broad and possesses a thin cuticle. Anteriorly an oblique depression is present, which functions as a sucking disc (fig. 19, _s_). Its edges are raised above the general surface and are contractile. It corresponds to a peristome and acts as an adhesive organ (fig. 20, _b_, _c_). No true cytostome is present. A double longitudinal ridge, representing axostyles, extends from the sucking disc to the tapering posterior extremity, which is prolonged as two flagella from 9 µ to 14 µ long.

_Lamblia intestinalis_ possesses eight flagella (fig. 19). The first pair of flagella, which cross one another, arise in a groove formed by the anterior edge of the sucking disc. Two pairs of flagella (lateral and median) are inserted on the posterior edge of the disc, while the posterior flagella occur at the tapering posterior extremity of the body. Basal granules are found at the bases of the flagella. The median flagella are most active in movement, the anterior and lateral flagella being less motile, as they are partially united to the body for part of their length.

The nuclear apparatus is situated in the thin, anterior, hollowed part of the body. It is at first dumb-bell shaped, the “handle” of the dumb-bell being formed by a very slight connecting strand, which eventually separates, so that the flagellate becomes binucleate, and thus completes the general bisymmetry of the organism.

There is a karyosome in each nucleus. Other bodies of unknown function, and possibly composed of chromatin, occur on or near the axostyles.

Division has not been observed in the flagellate stages of the Lamblia, but it occurs within the cysts. The resistant cysts (fig. 20, _e_) are oval and are surrounded by a fairly thick, hyaline cyst wall. They measure 10 µ to 15 µ by 7 µ to 9 µ, and may be tetranucleate. According to Schaudinn, the cysts arise from the conjugation of two individuals, and nuclear rearrangement occurs.

_L. intestinalis_ occurs in its flagellate stage in the duodenum and jejunum, and rarely as such in the other parts of the intestine. Normally it is found in the large intestine as cysts, which are voided with the fæces. The hosts of Lamblia include _Mus musculus_, _M. rattus_, _M. decumanus_, _M. silvestris_, _Arvicola arvensis_ and _A. amphibius_, the dog and cat, rabbit, sheep and man. Cysts voided with the fæces of infected animals reach plants or drinking water, and thence are transferred to man.

The flagellate in these different hosts exhibits some variation in size and in the problematic chromatic bodies. Bensen has suggested the species _L. intestinalis_ from man, _L. muris_ from the mouse and _L. cuniculi_ from the rabbit. It is not certain whether these different species are necessary, as the variation may be due to differences of environment.

Like Trichomonas, Lamblia can multiply under inflammatory conditions of the alimentary tract. Thus they are found in cases of diarrhœa, carcinoma of the stomach, etc. The parasites attach themselves by their sucking discs to the epithelial cells of the gut (fig. 20, _c_), and though their numbers may be very great, their direct pathological significance is not fully known. Their occurrence in cases of diarrhœa has been explained as being due to the increased peristalsis, which has detached the parasites from the epithelium. Free flagellate forms perish in stools if kept, more especially if the temperature falls below 0° C. or rises above 40° C. Lamblia has often been found in dysenteric diseases, especially in the East, and is said to be the causal agent of certain diarrhœas in India. Mathis (1914)[45] found Lamblia in cases of diarrhœa with dysenteriform stools in Tonkin. He also discovered healthy carriers of Lamblia cysts.

[45] _Bull. Soc. Med. Chirurg. Indo-Chine_, v, p. 55.

The parasite under discussion was first observed by Lambl (1859) in
the mucous evacuations of children. He regarded the parasite as a
Cercomonad and termed it _Cercomonas intestinalis_, which name as a
rule is applied to _Cercomonas hominis_, Davaine, although Stein had
already pointed out the difference between the two species. Grassi
(1879) observed this species first in mice (calling it _Dimorphus
muris_), and subsequently in human beings in Upper Italy and named
it _Megastoma entericum_. Bütschli and Blanchard then laid stress on
the identity of this species with Lambl’s _C. intestinalis_ (1859),
and consequently called it _Megastoma intestinale_. Later, Blanchard
drew attention to the circumstance that the generic name _Megastoma_
chosen by Grassi had already been used four times for various kinds
of animals, and established the genus _Lamblia_. Accordingly, _L.
intestinalis_ is the valid name, and should be generally adopted.

In Upper Italy the parasite in the encysted condition has also
been seen by Perroncito in man. At the same time, Grassi and
Schewiakoff began a new investigation of specimens from mice and
rats. In Germany, _L. intestinalis_ was found by Moritz and Hölzl,
Roos, Schuberg and Salomon. Moritz and Hölzl confirmed the relative
frequency of the species. In Königsberg, Prussia, a student found
encysted _Lamblia_ in his fæces. One case was reported from Finland
by Sievers, another case from Scandinavia by Müller. Frshezjesski and
Ucke reported cases from Russia. Jaksch announced the occurrence of
the parasite in Austria; Piccardi mentioned their presence again in
Italy. They were reported from Egypt by Kruse and Pasquale, and from
North America (Baltimore) by Stiles. Noc stated that 50 per cent. of
the population of Tonkin harboured _Lamblia_. Finally, the structure
of _L. intestinalis_ has been described by Metzner (1901), and by
Wenyon[46] (1907) in mice.

[46] _Arch. f. Protistenkunde_, Suppl. i, p. 169.

In all these cases _L. intestinalis_ has been observed in the small intestine, or in the evacuations of patients with intestinal diseases. It has also been found in the intestine of healthy subjects. Just as _Trichomonas intestinalis_ may be found inhabiting the stomach in diseases of that organ, in which an alkaline reaction is present (carcinoma), so has _L. intestinalis_ been found to occur under similar circumstances (Cohnheim, Zabel). However, in Schmidt’s case, 1 per cent. hydrochloric acid was certainly stated to be present. Infection takes place by the ingestion of cysts (fig. 20, _e_), as was established by Grassi, experimentally on himself. Cereal food-stuffs, contaminated with Lamblia cysts from vermin of the locality, such as rats and mice, serve to convey the infection to man. Such cysts may probably be found in street-dust, etc. Stiles induced infection in guinea-pigs, and Perroncito in mice and rabbits, by means of cysts of Lamblia from human beings. Stiles suspected that flies could transport Lamblia cysts. Mathis (1914) found that _L. intestinalis_ was not amenable to emetine, at any rate in its cystic stage.

Order. *Protomonadina*, Blochmann.

The smallness of the Protomonadines and their less superficial situation than the Polymastigines, may be the cause that so far as the species occurring in man are concerned, they were formerly less well known. As regards parasitic species, this group may be divided as follows, according to the number of flagella and the presence or absence of an undulating membrane:--

(1) _Cercomonadidæ_, with one flagellum at the anterior extremity, without an undulating membrane.

(2) _Bodonidæ_, with two flagella, without an undulating membrane, except in Trypanoplasma.

(3) _Trypanosomidæ_, with one flagellum, and an undulating membrane along the length of the body in some genera.

Family. *Cercomonadidæ*, Kent emend. Bütschli.

Small uniflagellate forms, without cytostome.

Genus. *Cercomonas*, Dujardin emend. Bütschli.

Oval or rounded organisms, with the aflagellar end often drawn out into a tail-like process.

*Cercomonas hominis*, Davaine, 1854.

Davaine found flagellates in the dejecta of cholera patients. They had pear-shaped bodies, lengthening to a point posteriorly. Their length was from 10 µ to 12 µ, and a flagellum about twice as long as the body projected from one extremity (fig. 21). A nucleus was hardly recognizable. Occasionally a somewhat long structure (cytostome?) appeared at the anterior extremity. The animals moved with remarkable activity. They also attached themselves by means of their posterior extremities and swung about around the point of attachment. Davaine found a smaller variety, only about 8 µ long, in the dejecta of a typhoid patient (fig. 21, _b_).

The Flagellata observed by Ekeckrantz (1869) in the intestine of
man belong to this form--at least to the larger variety--and Tham
(1870) reported fresh cases soon after. Lambl’s publication of 1875,
which was written in Russian, and became known through Leuckart’s
work on parasites, also alludes to apparently typical Cercomonads,
which, however, were discovered, not in the intestine, but in an
_Echinococcus_ cyst in the liver (fig. 22). The elliptical, fusiform,
rarely pear-shaped or cylindrical bodies of the parasites measured
5 µ to 14 µ in length, and were provided with a flagellum at one end,
while the other extremity usually terminated in a long point. An oral
aperture occurred at the base of the flagellum, and there were one or
two vacuoles near the posterior extremity. Longitudinal division was
also observed (fig. 22).

As already mentioned, this form, which Lambl termed _Cercomonas intestinalis_, differs considerably from the form found by the same author in 1859, which received the same designation (_cf. Lamblia intestinalis_, p. 60), but it corresponds with _Cercomonas hominis_, Davaine. The latter, as well as _C. intestinalis_, Lambl, 1875, is usually classed with the Trichomonads, but, as has already been remarked (_cf._ _Trichomonas intestinalis_, p. 54), this cannot be considered correct, as only _one_ flagellum is present.

_Cercomonas vaginalis_ (Castellani and Chalmers, 1909) was found in the vagina of native women in Ceylon.

Other species of _Cercomonas_ have, at various times, been recorded from man. However, the parasitic species of the genus _Cercomonas_ require further investigation.

According to Janowski (1896–7), typical Cercomonads have also been
observed in the intestine of man by Escherich, also by Cahen,
Massiutin, Fenoglio, Councilman and Lafleur, Dock, Kruse and
Pasquale, Zunker, Quincke and Roos, and others. However, it is an
open question whether the Flagellata observed by Roos in one of his
cases belonged to Davaine’s species, the size showing some deviation
(14 µ to 16 µ). In his, as in many other cases, doubts have been
raised as to whether the flagellates found in the stools had actually
lived in the intestine, or had subsequently appeared in the fæces:
for this a surprisingly short time only is necessary. Salomon also
appears to have observed Cercomonads (_Berl. klin. Wochenschr._,
1899, No. 46).

As with _T. intestinalis_ so with _C. hominis_, it appears that
the parasite settles not only in the intestine but also in the
air-passages. This is demonstrated by the statements of Kannenberg
and Streng of the occurrence of Monads and Cercomonads in the
sputum and putrid expectoration in gangrene of the lungs, which no
doubt apply to _C. hominis_ (_cf._ also Artault). Possibly also the
Flagellata observed in the pleural exudation by Litten and Roos may
be included here; this is the more probable in Roos’s case as the
process ensued in the pleura after the breaking through of a vomica.

Perroncito and Piccardi have described encysted stages of Cercomonads.

*Monas pyophila*, R. Blanch., 1895.

R. Blanchard thus designates a Flagellate that Grimm found in the
sputum, as well as in the pus of a pulmonary and hepatic abscess,
in the case of a Japanese woman living in Sapporo. The parasites
resemble large spermatozoa (fig. 23). The body, 30 µ to 60 µ, has
the shape of a heart or a myrtle leaf, and is surrounded by a thick
cuticle which is supposed to extend into the interior of the body,
dividing it into three parts. A long appendix at the rounded pole
is covered for the greater part of its length by the cuticle; the
extremity, however, is free and resembles a flagellum. The parasites
were very active, frequently changed their shape, and were able to
retract the long appendix within the body, which then assumed a round
form.

[This organism requires further investigation.]

Family. *Bodonidæ*, Bütschli.

_Protomonadina_ which are either free-living or parasitic, with two dissimilar flagella, while the possession of an undulating membrane and of a kinetic nucleus or blepharoplast is variable.

There are three genera:--

1. _Bodo_, Stein, 1878, without a kinetic nucleus and undulating
membrane.

2. _Prowazekia_, Hartmann and Chagas, 1910, with a kinetic
nucleus and without an undulating membrane.

3. _Trypanoplasma_, Laveran and Mesnil, 1901, with a kinetic
nucleus and undulating membrane.

Of these genera _Prowazekia_ must be discussed. _Bodo_ does not occur in man. Species of _Trypanoplasma_ occur in the blood and in the gut of various fishes, in the seminal receptacle of certain snails, in the gut and genitalia of a flatworm (_Dendrocœlum lacteum_) and in the vagina of a leech. Closely allied to _Trypanoplasma_ is the genus _Trypanophis_, parasitic in the cœlenteric cavity of Siphonophores.

Genus. *Prowazekia*, Hartmann and Chagas, 1910.

The genus was founded for a flagellate parasite, _Prowazekia cruzi_, discovered in a culture of human fæces in Brazil. Various other species have been referred thereto. The genus is separated from _Bodo_ by the possession of a second nucleus, the so-called kinetonucleus or blepharoplast. It differs from _Trypanoplasma_ in the absence of an undulating membrane. It is heteromastigote, that is, it possesses two dissimilar flagella, one anteriorly directed and the other lateral and trailing.

The principal species are:

*Prowazekia urinaria*, Hassall, 1859.

Syn.: _Bodo urinarius_, Hassall, 1859; _Trichomonas irregularis_,
Salisbury, 1868; _Cystomonas urinaria_, Blanchard, 1885; _Plagiomonas
urinaria_, Braun, 1895.

Hassall[47] in 1859 first found Bodo-like flagellates in human urine. He examined fifty samples of urine from patients suffering from albuminuria and from cholera. The reaction of the urine was alkaline or sometimes only feebly acid. The flagellates were only seen after the urine had been standing for several days. Hassall named the organism _Bodo urinarius_, and gave a very good description of it with illustrations. The flagellate, which was round or oval, measured 14 µ by 8 µ. The organism had “one, usually two, and sometimes three lashes or cilia.” In 1868 Salisbury described a similar flagellate in the urine under the name _Trichomonas irregularis_. Künstler in 1883 described the latter parasite under the name _B. urinarius_. In 1885 Blanchard, considering Künstler’s organism a different parasite from Hassall’s, called it _Cystomonas urinaria_. Braun, in 1895, gave the name _Plagiomonas urinaria_. Barrois (1894) considered Künstler’s and Hassall’s organisms to be identical and not to be true parasites of man. Sinton,[48] in 1912, found the flagellate in the deposit, after centrifuging, of a 24-hour old specimen of alkaline urine from a Mexican sailor in the Royal Southern Hospital, Liverpool. Sinton found a kinetic nucleus or blepharoplast in the organism, and therefore placed it in the genus _Prowazekia_.

[47] _Lancet_, 1859, ii, p. 503.

[48] _Annals Trop. Med. and Parasitology_, vi, p. 245.

The flagellate stage (fig. 24) of the organism is polymorphic, and may be either (_a_) sausage-shaped, 10 µ to 25 µ in length by 2·5 µ to 6 µ in breadth; (_b_) round or oval, varying from 4 µ in diameter to oval forms 15 µ by 10 µ; (_c_) a carrot-shaped form, of varying size up to 25 µ by 4 µ. The kinetic nucleus is large and pear-shaped. Near it are basal granules, closely applied to one another, from which the flagella arise. There is a small cytostome near the roots of the flagella. There is a well-marked karyosome in the nucleus. The movement is jerky. The shorter, anterior flagellum may be used in food-capture. In life, bacteria have been seen to be ingested. Food-vacuoles tend to accumulate at the posterior (aflagellar) end. A contractile vacuole may be present, near the base of the cytostome, and may really be the dilated fundus of the latter. Division occurs by binary fission. The organism can encyst (fig. 25, _a_), when the flagella are lost, and round or oval cysts are found, 5 µ to 7 µ in diameter. After a time flagella are formed inside the cyst, and the organism emerges therefrom in its typical flagellate form (fig. 25, _b_-_f_).

Sinton’s case is interesting. He obtained the flagellate only twice from the same patient, a Mexican then in hospital in Liverpool. The flagellate was not found in the patient’s fæces, nor was it found in the urine on later occasions when taken aseptically.

In cultures _Prowazekia urinaria_ was always found in association with bacteria. The cultures died at a temperature of 37° C., but grew well at 20° C. Various media were useful at the lower temperature, such as urine, salt agar, nutrient agar, serum agar, blood agar, peptone salt solution, and diluted blood serum. The flagellate was, then, considered to be an accidental contamination and not a true parasite of human urine.

*Prowazekia asiatica*, Castellani and Chalmers, 1910.

The flagellate was found by the discoverers in the stools of patients suffering from ankylostomiasis and diarrhœa in Ceylon. It was referred by them to the genus _Bodo_, but in 1911 Whitmore[49] further studied it and placed it in the genus _Prowazekia_. In the stools the flagellate is found either as a long, slender form measuring 10 µ to 16 µ by 5 µ to 8 µ or as a rounded form 8 µ to 10 µ in diameter. Its cytoplasm is alveolar. A rhizoplast connects the basal granules to the kinetic nucleus. There is multiplication and cyst formation as before. The organism is easily cultivated, especially in the condensation water of nutrose agar and maltose agar. The pathogenicity is stated to be nil.

[49] _Arch. f. Protistenk._ xxii, p. 370.

*Prowazekia javanensis*, Flu, 1912.

Found in agar cultures from the motions of patients at Weltevreden, Dutch East Indies.[50] The flagellates are 12 µ long and 5 µ broad. The lateral flagellum is stated to be attached to the cell body for a short distance. Regarding the karyosome in the nucleus, the author states that the smaller the karyosome the more chromatin is deposited on the nuclear membrane. Flu mentions that the specific name _javanensis_ is a temporary one, as in the course of time it may be shown that there is only one species of _Prowazekia_.

[50] _Geneesk. Tijdschr. v. Nederl. Ind._, lii, p. 659; _Med. v. d. Burg. Geneesk. d. Nederl. Ind._, iii, p. 1.

*Prowazekia cruzi*, Hartmann and Chagas, 1910.

Found in a culture from human fæces on an agar plate in Brazil, and considered to be a free-living form.[51] The organism is oval or pear-shaped, 8 µ to 12 µ long and 5 µ to 6 µ broad. In human stools at Tsingtau, China, a _Prowazekia_ has been found by Martini which he thinks is the same as _Prowazekia cruzi_. He considers it to be a cause of human diarrhœa and intestinal catarrh.

[51] _Mem. Inst. Osw. Cruz._, ii, p. 64.

*Prowazekia weinbergi*, Mathis and Léger, 1910.

This species was found in the fæces of men, both healthy and diarrhœic, in Tonkin.[52] It is pear-shaped, 8 µ to 15 µ long by 4 µ to 6·5 µ broad. The flagella occur at the broad end.

[52] _Bull. Soc. Med. Chir. Indo-Chine_, i, p. 471.

The discoverers think that _Prowazekia weinbergi_ is an intestinal inhabitant, but non-pathogenic, since it was found to occur in the fæces even when obtained with aseptic precautions.

*Prowazekia parva*, Nägler, 1910.

A free-living form found in the slime on the stones at the biological station at Lunz. Another _Prowazekia_ was found in 1914 in tap-water in Calcutta.

Family. *Trypanosomidæ*, Doflein.

The Trypanosomidæ, broadly considered, are uniflagellate organisms, the flagellum being at the anterior end. The flagellum arises near the blepharoplast (kinetic nucleus), which lies anterior, near or posterior to the nucleus.

The following genera will be considered:--

_Trypanosoma_--with an undulating membrane along the length
of the body.

_Crithidia_--with a less well-developed undulating membrane
anteriorly (see fig. 49).

_Herpetomonas_--including the so-called _Leptomonas_, with anterior
free flagellum only, and no undulating membrane.

_Leishmania_--non-flagellate forms in mammalian blood, flagellate
herpetomonad stages in culture, probably occurring
naturally in Arthropods.

Genus. *Trypanosoma*, Gruby, 1843.

The members of the genus possess a single flagellum, which arises posteriorly, adjacent to a blepharoplast or kinetic nucleus. The flagellum forms a margin to an undulating membrane, and may or may not be continued beyond the body as a free flagellum. Many species are parasitic in vertebrate blood and in the digestive tracts of insects.

HISTORICAL.

The history of blood flagellates goes back to the year 1841, in which
Valentin discovered in the blood of a brook-trout (_Salmo fario_ L.)
minute bodies, from 7 µ to 13 µ in length, with active movements and
presenting marked changes in form. Valentin considered the parasite
a new species of the old genus _Proteus_ or _Amœba_, Ehrbg. This
announcement led Gluge (1842) to publish a similar discovery he had
made in frog’s blood. The latter forms were called by Mayer (1843)
_Amœba rotatoria_, _Paramœcium loricatum_ and _P. costatum_, while
Gruby (1843) called them _Trypanosoma sanguinis_.[53] Later it was
discovered that similar organisms occurred also in the blood of birds
(Wedl (1850), Danilewsky) and of mammals. Gros (1845) found them in
the mouse and mole, Chaussat (1850) in the house rat, Lewis (1879) in
the Indian rat, Wittich (1881) in the hamster. Danilewsky (1886–89)
and Chalachnikow (1888) investigated the structure and division of
trypanosomes.

[53] Gruby’s generic name is generally accepted. Still others have been used, _e.g._, _Undulina_, Ray _Lankester_, _Globularia_ Wedl, _Paramecioides_ Grassi, _Trypanomonas_ Danilewsky, _Hæmatomonas_ Mitrophanow.

In the case of all these forms, there was no discussion as to a
pathogenic influence on the host. Opinion, however, as to the action
of trypanosomes changed when, in 1880, Evans found flagellates in
the blood of horses in India that suffered from a disease endemic
there called “surra,” and associated the parasites with the disease.
Steel and Evans were successful in transmitting the parasites--first
known as _Spirochæta evansi_, Steel, then as _Trichomonas evansi_,
Crookshank, and finally as _Trypanosoma evansi_--to dogs, mules and
horses. They recognized that the above mentioned flagellates in the
blood of the experimental animals were the causal agents of the
disease.

From that time there was a considerable increase in the literature,
the contents of which have been summarized by Laveran and Blanchard.
In 1894 Rouget discovered trypanosomes in the blood of African horses
that suffer from “stallion’s disease” (dourine). In 1894 Bruce
found similar forms (_T. brucei_) in the blood of South African
mammals suffering from “nagana,” and in consequence attention was
drawn to the part which the much dreaded tsetse-fly played in the
transmission of “nagana.” In 1901 Elmassian discovered trypanosomes
in the blood of horses that were stricken with “mal de caderas,”
which is very common in the Argentine. The disease in cattle named
“galziekte” (gall-sickness), occurring in the Transvaal, was also at
one time attributed to a trypanosome remarkable for its great size,
and like some other species, bearing the name of its discoverer (_T.
theileri_).

The study of the species hitherto known has been carried on partly
by the above mentioned authors and in part by others, _e.g._,
Rabinowitsch and Kempner, Laveran and Mesnil, Wasiliewski, Senn.
It was greatly advanced by the method of double staining (with
alkaline methylene blue and eosin) introduced by Romanowsky (1891)
and elaborated by Ziemann, Leishman, Giemsa and others. By this means
the presence of a terminal flagellum and of an undulating membrane
at the side of the flattened and extended body was demonstrated.
Laveran and Mesnil (1901) discovered allied flagellates in the blood
of the fish, _Scardinius erythrophthalmus_. These flagellates, now
placed in the genus _Trypanoplasma_, had a second free flagellum in
addition to the one bordering the undulating membrane. Trypanoplasms
have since been found in both freshwater and marine fishes. The
transmission of trypanoplasms of freshwater fishes is effected by
leeches. _Trypanoplasma varium_ from _Cobitis_ is transmitted by
_Hemiclepsis marginata_ according to Léger, while the Trypanoplasmata
of _Cyprinus carpio_ and _Abramis brama_ reach new hosts by the
agency of _Piscicola_ according to Keysselitz.

Another ally of the Trypanosomidæ, _Trypanophis_, lives in the
cœlenteric cavity of Siphonophores. It has also an extra terminal
flagellum (Poche, Keysselitz). [_Trypanoplasma_ and _Trypanophis_
belong to the _Bodonidæ_, see p. 63].

Finally it was shown that Trypanosomes occurred in human beings.
Although Nepveu’s early report of trypanosomes in the blood of
malarial patients may be doubtful, subsequent researches by Forde
and Dutton demonstrated trypanosomes (fig. 28) in the blood of a
European, apparently suffering from malaria, living in the Gambia.
Dutton (1902) called the human trypanosome, _T. gambiense_. The
expedition despatched by the Liverpool School of Tropical Medicine
(1902) to Senegambia found trypanosome infections in six cases among
a thousand inhabitants examined.