known as hcematozoa. Parasites of the red blood-cor-
puscles have been met with abundantly in the blood of
fish, turtles, and many species of birds.
The relation of the different forms of the malarial
parasite to each other and to the varieties of the disease
are still under discussion. Galgi, Marchiafava and
other Italian observers hold that they are distinct
varieties, not interchangeable, though closely allied
biologically. Laveran, on the other hand, contends for
the unity of the forms, which he regards as modifica-
tions of one polymorphic parasite. But with the
present imperfect knowledge of the full life-history of
the parasite the question cannot be considered as settled.
The following varieties are associated with the differ-
ent forms of malarial fever :
I. Parasite of the Simple Intermittent Fever, (a) TER-
TIAN PARASITE (see Plate II.). If the blood of a
patient be examined during or shortly after the chill
in tertian fever, inside the red blood-corpuscles, or less
often free in the plasma, will be seen small, pale, hya-
line amoebae which undergo rapid changes in shape,
often assuming the form of a star or of a cross. There
may be no pigment visible, and to these hyaline bodies
Marchiafava and Celli gave the name plasmodia. In a
few examples scattered pigment granules may be seen
in the amcebse, usually placed near the periphery. In
628 APPENDIX.
dry specimens these bodies stain deeply with methylene-
blue, and they are solid or vesicular in form. If the
examination be made within twelve to eighteen hours
after the chill the hyaline bodies are seen to have
grown to occupy one-fourth to one-third of the bodies
of the red cells. They are more pigmented, and the
corpuscles containing them have become gradually paler
and somewhat expanded. The pigment granules, which
at first are small, increase in size, and the organisms
show very active amoeboid movements. At the end of
forty-eight hours they occupy entire corpuscles, are very
sluggish in their movements, and look like thin, trans-
lucent shells, and are usually devoid of color. Many
of the organisms then undergo the remarkable change
known as segmentation, which precedes and is asso-
ciated with chills and fever. The amoeboid movement
ceases as well as that of the pigment granules. The
latter gradually collect toward the centres of the amoebae
until they are in the form of closely packed, more or less
central clumps. The protoplasm becomes more finely
granular, and indistinct lines of striation are seen, which
begin at the periphery. At this stage the organisms
may present the appearance of rosettes. The segmen-
tation progresses until the entire protoplasm is divided
into twelve to eighteen or twenty spheres. The shell
of the corpuscles containing a parasite usually bursts,
and the small, rounded, hyaline bodies are set free.
Each one of these little bodies consists of a translucent
protoplasm, with a central, more highly refractile spot.
In stained preparations, during the segmenting process,
the reticulum becomes denser and sharper, and then
breaks up into fifteen to twenty small spheroidal
spores.
PLASMODIUM MALARIJE. * 629
The segmentation is regarded as a reproductive pro-
cess, and these small spherical bodies are believed to
be the spores which penetrate a new set of corpuscles,
and so begin a new cycle of development. The pig-
ment is discharged into the plasma, and partly taken
up by the leucocytes. It is finally lodged chiefly in
the spleen, liver, and lymphatic organs. The pres-
ence of the segmenting forms is invariably associated
with the paroxysm. On finding them in the blood it
can be predicted with certainty that a paroxysm is
imminent. In quotidian fever we have to deal with
two groups of tertian (or three groups of quartan) para-
sites, maturing on successive days; and the full-grown
segmenting forms of to-day's paroxysms and the half-
grown organisms of to-morrow's attack are to be found
in the blood.
(b) QUARTAN PARASITE (see Plate II.). The early
forms within the red blood-corpuscles are amoeboid
bodies, similar to those of tertian fever. Soon, how-
ever, it is noticed that the pigment is different ; the
granules are larger and blacker, and the amoeboid
movements are not so active. In their growth the
parasites do not decolorize the corpuscles, which some-
times have a greenish, brassy look. From the sixty-
fourth to the seventy-second hour the amoebae have
reached their full development, occupying the greater
portion of the affected corpuscles ; but a thin rim of
colored stroma can usually be seen. Some of the cor-
puscles are completely filled by the parasites. The
cells, as a rule, appear shrunken rather than swollen.
Even at this stage a skilled observer can usually
recognize the quartan from the tertian organism. The
pigment granules then collect toward the centre, and
630 APPENDIX.
in so doing usually form distinct rays. Then, as in
the tertian form, the organism begins to segment ; a
marginal indentation is first seen, with lines of radia-
tion, and a beautiful rosette is formed, which segments
into from six to ten, occasionally twelve, small, spher-
ical or ovoid bodies. The character of the pigment,
the smaller size of the organism, and the development
are differences which separate the quartan from the
tertian variety.
In the quartan malarial fever the blood may show
two or more groups of parasites. There may be two
groups which reach maturity on successive days, with
one day interval double quartan fever; or there may
be three groups of organisms maturing on successive
days, causing daily paroxysms triple quartan fever.
II. The -ffistivo-autumnal Parasite (see Plate II.).
In the more irregular and as a rule pernicious types
of malarial infection which are met with in the autumn
months a third variety of organism may be recognized,
which has been specially studied by the Italian obser-
vers. The youngest forms of this parasite are small
hyaline bodies about one-sixth the diameter of the red
cell. At first they are quiescent, but later develop
active amoeboid movement. They are at this stage
not unlike those of the tertian varieties; but the hya-
line body is more signet ring-like, more highly refrac-
tile, and the central part often looks shaded, as if a
more solid body were enclosed within a vacuole. As
this form increases the amoeboid movements are well
seen. The pigment is in small amount, at first in the
form of one or two very dark granules at the margin
of the amoebae, and the pigment never becomes so
abundant as in the tertian or quartan forms. The
PLASMODIUM MALARIJE. 631
organism rarely occupies more than about one-third of
the corpuscle, the stroma of which is never entirely de-
colorized. On the contrary, it often presents a curious
brassy-green appearance, and looks shrunken or crum-
pled. The cycle of development of this form is rarely
carried out entirely in the circulating blood, but the
bodies with centrally placed pigment are not uncom-
mon. The observations of the Italian observers seem
to show conclusively that the segmentation takes place
in the spleen and in the bone-marrow and internal
organs. The length of its cycle of development has not
been determined. Probably different groups mature at
varying intervals of time, from twenty-four hours or
less to forty-eight or more (Welch). The fever associ-
ated with this organism is characterized by irregularity,
the paroxysms are not at definite periods, and the
pyrexia may be more or less continuous, with remissions.
This form is associated with the severer types of the
malaria seen in late summer and autumn the sestivo-
autumnal fevers of Cuba, Italy, etc.
There are several other points of interest about the
parasites. A corpuscle containing a half -grown organism
may suddenly rupture; the haemoglobin diffuses, and
the pigmented parasite is set free. The parasite may
break up into two or three portions, perhaps from
pressure on the slide, and slight amoeboid changes may
be seen. In other instances, apparently from certain
free extra-corpuscular organisms, the remarkable flagel-
late form develops itself. The pigment becomes more
central, and the granules dance with great activity.
Suddenly, long, thread-like processes extend from the
body of the parasite and display remarkable move-
ments, thrashing about over the corpuscle with extra-
632 APPENDIX.
ordinary rapidity. A flagellum may break off from
the main body and move about independently among
the corpuscles. While these flagellate bodies appear
in both the tertian and quartan fevers they are very
much more numerous in the irregular malaria. The
significance of the flagellate form is still under discus-
sion. By some it has been regarded as a degenerate
form.
In the sestivo-autumnal, quotidian, or pernicious mala-
rial fevers there is developed also a very striking body,
to which much attention has been paid, viz., the <e cres-
cent " of Laveran. In any case of irregular malarial
fever which has lasted a week or more these bodies are
to be found. They are developed within the red blood-
corpuscle, the margin of which may usually be seen on
the concave surface of the crescent. The border is very
sharply defined, the protoplasm uniform, homogenous,
with coarse pigment granules, often in the form of rods,
which are collected about the centre. Bodies similar
in structure, but differing in form, being ovoid and
rounded, are also met with ; and the change of a cres-
cent into an ovoid or rounded body can be traced, which,
in turn, may in some instances be seen to project flagella
or form a flagellated body similar to that derived from
the extracorpuscular organisms above referred to.
Most authors say that both kinds of flagellate bodies
do not develop unless the blood be exposed to the air,
but an exposure of one or two minutes gives the best
results. It would seem that they do not exist as flagel-
late forms in the circulation. (Osier, in Allbutt's Sys-
tem of Medicine.)
Pigmented Leucocytes. Typical pigmented leucocytes
are very characteristic signs in malarial blood, and on
PLASMODIUM M ALARMS. 633
their presence alone the diagnosis must often rest: (1)
In severe acute cases after the administration of much
quinine; (2) in remittent malarial fevers; and (3) in
chronic malarial fever and cachexia. They persist in
the blood long after all traces of parasites have dis-
appeared. The identification of free malarial pigment
is usually hazardous, and the diagnosis of malaria
should never be based on its presence alone (Ewing).
Inoculation Experiments. Malarial infection can be
transmitted directly from man to man by subcutaneous
or intravenous inoculation of malarial blood. This was
shown first by Gerhardt in 1884. Later experiments,
chiefly by Italians observers, have confirmed Gerhardt 7 s
investigations, and almost in every instance the variety
of organism introduced has been reproduced. It has
also been experimentally shown that the ague paroxysm
is associated with the segmentation of enormous groups
of intracorpuscular amoeba?, the symptoms being prob-
ably due, as Bacelli suggests, to toxins liberated during
sporulation or to substances set free in the blood by
the rapid destruction of a large number of its corpuscles.
The period of incubation is from eleven to twelve days
in the regular intermittents and from two to five days
in the irregular autumnal fever.
Active phagocytosis goes on in all forms of malarial
infection, but its true significance is still undetermined.
That many parasites are devoured by the leucocytes,
especially in the spleen, is certain. This apparently
takes place during or after sporulation. But sponta-
neous recovery may also be due to the death of the
plasmodia. It is not improbable, however, that the
phagocytes contribute to the process of recovery, even
if they are not the chief factors in it.
634 APPENDIX.
With regard to immunity, we know that one attack
of malaria may linger a long time, and seems rather to
favor than to prevent a new infection. There is,
however, a natural susceptibility to the disease which
is very variable. Different races of men especially
seem to possess in variable degree the power of resist-
ance to malarial infection. This is shown not only in
a diminished tendency to contract the disease, but also
in the form by which they are affected. For instance,
the negroes in the Southern parts of the United States
are much less liable to contract malaria than the whites;
and Martin reports that the Europeans living in Suma-
tra are far more frequently and severely affected by
malaria than the natives, who, if they are attacked at
all, it is only with the simple intermittent tertian and
quartan fevers.
The Action of Quinine on the Parasites. Laveran
showed that a solution of 1 to 10,000 of quinine, run
under the cover-glass, would check at once the move-
ments of malarial organisms. As demonstrated by
Marchiafava and Celli, however, a like effect is pro-
duced either by the water or by the salt solution in
which the quinine is dissolved, and we meet with an
almost insuperable difficulty in the study of the direct
action of the drug upon the parasites themselves.
Many careful experiments have been made to deter-
mine the effect of quinine on the parasites circulating
in the blood, and Romanowsky, Golgi and others have
reported a diminution in the activity of the amoeboid
movements. Osier stated that, as a result of careful
hourly examinations made in a series of cases with a
view of ascertaining the direct influence of full doses of
quinine, he was unable to make up his mind that any
PLASMODIUM MALARIA. 635
particular change took place in the intracorpuscular
tertian parasite while undergoing destruction by the
specific.
The following points, nevertheless, about the action
of quinine on the parasites seem to be well established :
First, that under its use the intracorpuscular varieties,
whether tertian, quartan, or sestivo-autumnal, rapidly
disappear from the circulating blood; second, that
quinine administered some hours before a paroxysm
will not interrupt the cycle of their development, but
will usually destroy the products of segmentation, and
so check the succeeding paroxysm; third, that the cres-
centic and ovoid bodies which develop in sestivo-
autumnal fevers are very slightly affected by the action
of quinine.
Mixed Infection in Malarial Fever. It is now a well-
known fact that along with a malarial infection there
may exist another due to the typhoid bacillus, to one
of the pyogenic cocci, or to other micro-organisms.
Such mixed infection may make a complete diagnosis
a very difficult matter.
Diagnosis. The diagnosis of malaria in all its forms
has been greatly simplified by Laveran's discovery.
This is not a matter of so much importance in the
simple typical intermittents, but in the atypical forms
of the disease, and especially in pernicious malaria, the
symptoms of which are readily overlooked, serious
errors in diagnosis may be made. Moreover, par-
oxysms of intermitting fever, which are common in
other diseases, may be mistaken for those of malaria
such as occur in the early stages of tuberculosis, in
ulcerative endocarditis, in suppuration associated with
septicaemia or pyaemia, in pyelitis; etc. In all such
636 APPENDIX.
cases, and in cases of mixed malarial infection occur-
ring in malarial regions, a careful blood examination
enables a positive diagnosis to be made in a large
majority.
Technique of Blood Examinations for Malaria. The
finding of the parasite should not prevent us from
seeking farther in doubtful cases by means of the
Widal reaction and blood cultures for other infections
which may exist along with the malaria.
The parasites require a proper technique and a
certain experience for their recognition. The fresh
blood, when it can be obtained, should be examined,
but if no bodies be found, stained preparations should
always be later searched through; the drops may be
taken either from the tip of the finger or from the
lobe of the ear. It is important to have a perfectly
clean cover-glass and slide, and to cleanse the skin
thoroughly and to wipe it dry, so as to avoid dirt and
perspiration. A very small drop should be taken, and
care must be exercised that the cover-slips, when pressed
against the blood-drop, do not touch the skin. The
drop should be so small that the corpuscles are spread
out in a uniform layer and are not in rolls when the
cover-glass is laid upon the slide, for the intracorpus-
cular form cannot be well seen unless the blood-disk
presents the flattened surface. For making permanent
preparations the blood is collected upon cover-glasses
in very thin films, which should be instantly dried.
The blood-cells are fixed by immersion in equal parts
of alcohol (95 per cent.) and ether for fifteen minutes,
or by exposing for five minutes over a wide-mouthed
bottle containing 25 per cent, solution of formalin, or
by heating to 120 C. for ten minutes. Ewing advises
PLASMODIUM MALARIA. 637
the alcohol and ether method. The preparations are
stained with methylene-blue, or, if desired, with a
double stain of methylene-blue and eosin. The prep-
aration is covered with a mixture made of equal parts
of a saturated alcoholic solution of eosin and water for
one minute ; wash in water and dry in air. The prep-
aration is then covered by a saturated watery sol ution of
methylene-blue for a minute or two, washed in water,
dried, mounted, and examined with the immersion lens.
Thorough drying after the eosin staining makes the
blue stain of the parasites sharper (Ewing).
In some cases of sestivo-autumnal fever the para-
sites are chiefly in the spleen, liver, and bone-marrow.
The blood withdrawn directly from the spleen may
show large numbers, although in the circulating blood
they may be scanty. In these cases puncture of the
spleen and examination of the blood withdrawn may
render the diagnosis more certain, but in acute splenic
tumor the procedure is not without risk. The finding
of malarial parasites in the blood not only separates the
intermittent, continued, and remittent malarial fevers
from all other diseases in which similar fevers may
occur, but the variety of parasites found influences the
prognosis of the malarial infection. The number of
parasites observed on examination also influences the
prognosis to a certain degree, though too great weight
should not be laid on this point, particularly as the
result of a single examination. Whether there are any
forms of malarial infection in which there are no plas-
modia present in the circulating blood is a question
for future determination. We know that in all severe
seizures, if the blood is examined within twenty-four
hours of the beginning of the paroxysms and before
638 APPENDIX.
much quinine is given, the plasm odia can readily be
found, usually in considerable numbers. In some very
mild initial paroxysms the plasm odia may be difficult
to find. In aestivo-auturnnal malaria, while quinine is
being administered, there may be no organisms during
the period between the second and fourth day, but on
the fourth or fifth day the crescents almost always make
their appearance, notwithstanding the use of quinine
(Ewing).
Mode of Infection. It is generally acknowledged
that the most common mode of infection in malaria
is through the air. Whether the disease may be
directly conveyed by water has been much disputed.
Many favor the view, but experimental evidence is
distinctly against it. Persons have been allowed to
drink water from the Pontine marshes without ill
effects, and in Bacelli's clinic at Rome experiments
were made in thirty cases with water from malarial
districts without a single positive result. Grassi could
not produce the disease with dew from malarial regions
or by allowing healthy men to drink blood from mala-
rial patients. We may therefore assume that malarial
infection is not produced, as a rule, by way of the in-
testines. Numerous experiments have shown, oir the
contrary, that the infection may be induced by subcu-
taneous inoculation. It is quite conceivable, therefore,
that under natural conditions malarial infection may be
produced by way of the skin, and possibly by the bites
of insects. This is all the more probable, as certain
varieties of mosquitoes, in malarial regions, have been
found to be laden with the plasmodia. In another wide-
spread disease produced by blood parasites Texas fever
in cattle it has been shown that the amoebae are con-
PLASMODIUM MALARIJE. 639
veyed by means of the cattle tick from animal to animal.
The further the investigations have been pushed the
closer becomes the connection between mosquitoes and
malarial infection in man. So far as we know, a few
varieties of mosquitoes and man are the only places
where the malarial parasites develop, and Koch, fol-
lowing lines suggested by the work of others, has
now shown that the fresh cases of infection with
malaria occur only in warm weather when the parasites
can develop in the mosquitoes. Koch's idea is that
human beings having chronic malaria preserve in their
blood the malarial parasites during the cool months.
In the warm weather mosquitoes become infected, the
parasites develop in them and are present in their
poison sacs. These mosquitoes bite and infect fresh
human cases through subcutaneous inoculation. He
believes if we would treat all chronic malarial patients
with quinine so as to prevent the development of the
parasites and thus the infection of the new crop of
mosquitoes, we would prevent most, at least, of human
infection.
Blood parasites are extremely common in cold-
blooded animals, fish, reptiles, and in birds. .Birds
appear to suffer from malarial infection similar to that
in man, and the parasites found in the blood-corpuscles
are closely allied to those of human malaria. But in
birds infection cannot be produced by subcutaneous or
intravenous inoculation with parasites from human
blood, nor can infection be transmitted from birds to
man. The blood parasites found in fish and reptiles,
though similar to, are not identical with, those found
in man, and they are not transmissible to man. This
source of infection may, therefore, be excluded. Ex-
640 APPENDIX.
perience shows that the disease is Dot contagious, in
the ordinary sense of the word, and that it is not
directly transmitted from man to man.
AMCEBA COLI (Amoeba Dysenteriae of Councilman and
Lafleur; Dysenteric Amoeba).
In 1875, Losch, of St. Petersburg, gave the first
accurate description of an amoeboid organism which
he found in the stools of a dysenteric patient, and to
it he gave the name amoeba coli. He claimed that this
organism is the cause of dysentery, and he succeeded in
producing a superficial ulceration of the large intestine
in one of four dogs which had received rectal injec-
tions of the dysenteric stools. Losch' s observation
has been confirmed by various researches in different
countries.
Morphology. The amoeba is a unicellular organism
belonging to the class of rhizopada of the protozoa,
and consists of slightly differential masses of proto-
plasm, which, under favorable circumstances, exhibits
spontaneous movements. In a state of rest the amoeba
assumes a spherical shape which appears discoid in the
field of the microscope. It may generally be distin-
guished from the other cellular elements found in the
feces by its pale greenish tint and by its stronger
refraction of light. Its diameter varies within wide
limits, 6// to 35// 7 more commonly between 12// and
26//. It is noteworthy that such differences in size
are found, as a rule, in different cases of the disease,
while the amoebae in any individual case are nearly
uniform in diameter. The body of a resting amoeba
has a well-defined, regular body, which, under ordi-
nary conditions, appears as a thin, single, dark line.
PLATE II.
v
o
Figs, i, 2, and 3 show three phases of the parasite of tertian fever.
Fig. i, ring form, showing beginning pigment formation. Fig. 2, full-
grown parasite. Fig. 3, segmenting bodies. (WELCH and THAYER.)
Figs. 4, 5, and 6 show the parasite of quartan fever at different stages
of growth. Fig. 4, moderately developed intracorpuscular parasite. Fig. 5,
large swollen extracorpuscular form. Fig. 6, flagellate body.
(WELCH and THAYER.)
Figs. 7, 8, and 9 illustrate the sestivo-autumnal parasite. Fig. 7, ring-like
body, with a few pigmented granules. Fig. 8, crescent still in blood-cor-