and that of other Italians. I was particularly struck by the phenomena
of exflagellation and more particularly by the fact that it occurred
only when the blood had been removed from and was outside the human
body. I reasoned that if this exflagellation occurs only outside the
body, the purpose of the flagellated body must lie outside the human
body, and that therefore the flagellated body must be the first phase
of the malarial parasite outside the body, must be the first step that
the malarial parasite takes in passing from one human host to another.
There seemed to me to be a sort of logic in this. But how was the
malarial parasite to pass from one human being to another? It was not
provided while inside the human body with any organs of locomotion or
penetration; as far as we know the parasite is never extruded in the
excreta, neither does it habitually escape in hæmorrhages. Therefore,
the idea of a spontaneous escape of the parasite from the human body
had to be dismissed. I therefore concluded that some extraneous agency
must remove the parasite from the human body, so as to afford the
opportunity for this flagellation which I had concluded must constitute
the first step in its extra-corporeal life. In casting about for an
organism which could effect this removal I, for many reasons similar
in some respects to those that influenced the savage African, the
Italian peasant, King, Laveran and others, came to the conclusion
that the medium of removal and transit must be the mosquito. I was so
impressed with the probabilities of this double hypothesis and with
its extreme practical value, should it prove to be correct, that I
endeavored to leave England for a time and to visit British Guiana
or some such suitable malarial country where I might work out the
idea. Unfortunately, that could not be accomplished, so I published
my theory in the hope that it would appeal to someone who might enjoy
the opportunities denied to me. At that time Surgeon-Major Ross was
at home from India and we had many conversations on the subject. I
described to him my hypothesis, the probabilities of which and the
possibilities of which powerfully appealed to his highly logical and
practical mind. He undertook, when he returned to India, to do his best
either to establish or confute it. Accordingly he set to work in India
experimenting with mosquitoes and malaria.
Ross was stationed in Secunderabad, in the south of India, where there
was abundant opportunity for experimental work--plenty of patients and
plenty of mosquitoes. He got patients with crescent parasites in their
blood and he got mosquitoes to bite them. He found that in the course
of a few minutes after the blood had entered the insects’ stomachs the
crescent parasites proceeded to the formation of sphere and flagellated
body. But he got no further. This experiment was repeated hundreds of
times. Many of his preparations were sent to me, and I could confirm
from them the accuracy of his statements on the subject. Ross was
encouraged, for obviously we were on the right track. One day Ross,
whose station had in the meantime been changed, caught some mosquitoes
which had been feeding on a patient the subject of tertian malaria.
He kept the mosquitoes and after a few days dissected them. He took
the stomach out and placed it on a slip with a little salt solution,
covered it with a cover-glass and examined it with a microscope. He
was gratified to find lying amongst the transverse and longitudinal
muscular fibres a number of spherical bodies, very sharply defined,
and including a great many grains of intensely black pigment exactly
like those of the malaria parasite. Ross was at once struck with the
similarity. After years of labor he believed he had at last seen the
malaria parasite in the tissues of the mosquito, where we reasoned
it ought to be; and he was right. At a subsequent experiment on the
malarial patient he found exactly the same bodies, and on dissecting
several mosquitoes at different intervals of time he found that the
parasite, which originally was six micro-millimetres in diameter
only, grew to sixty or eighty micro-millimetres, each parasite,
notwithstanding its growth and the lapse of time, still containing the
peculiar and most characteristic black pigment. Ross was now quite sure
that he had found the extra-corporeal phase of the malarial parasite.
Some of these preparations he sent home. I examined them and showed
them to a number of friends in London familiar with the malarial
parasite; they agreed with me, as Laveran also did, in believing that
probably this indeed was the long-sought-for extra-corporeal phase
of the malarial parasite. Ross at that time had great difficulty in
getting opportunities for experiment on the human subject and in
procuring proper mosquitoes. He found that the mosquitoes in which
he had discovered these pigmented bodies were of a different species
to those on which he had formerly experimented, and that in this
circumstance lay the explanation of his lack of success earlier as
well as the secret of his ultimate success. Failing to get sufficient
opportunity for experimenting on human malaria he turned to bird
malaria. He found that the sparrow of Calcutta, in a large proportion
of instances, contained in its blood a malaria-like parasite. Ross
procured a number of infected sparrows and let loose upon them a number
of mosquitoes of a species belonging to the genus _culex_. These
mosquitoes, after from one to ten days, he dissected and examined their
stomachs. He found in the stomach-wall pigmented bodies exactly similar
to those which he found in the stomach-walls of mosquitoes fed on human
malarial blood. He found that they increased in size and in a week or
ten days grew from six to eighty micro-millimetres in diameter. When
they became of considerable size they protruded like warts from the
surface of the insect’s stomach and were included in a very definite
capsule. At this stage the capsule was filled with a vast number of
very minute rod-like bodies. These capsules, which now projected into
the body cavity of the insect, being over-distended, ruptured and
discharged the rod-like bodies into the body cavity of the mosquito.
For a time Ross could get no further than this. He could not find what
became of the rod-like bodies. One day, in dissecting the head of a
mosquito, he encountered two small trilobed glands the ducts from
which united to form a main duct. The glands lay on either side of the
head and the common duct he traced to the base of the proboscis of the
mosquito. This was the salivary gland of the mosquito. He found that
the cells of the gland contained rod-like bodies exactly like those
which he had found inside the parasitic capsules in the stomach-wall.
He concluded that somehow these ‘germinal rods’ (for so he called
them) had managed to find their way into the salivary gland of the
mosquito. It immediately occurred to him that this might be the route
by which the parasite escaped from the mosquito into its vertebrate
host. No sooner had the idea occurred to Ross than he put it to the
test of experiment. He selected a number of sparrows in whose blood
he satisfied himself that there were no parasites and let loose upon
them a number of mosquitoes which he had already infected with malarial
parasites. He found after a week or ten days that the sparrows which
were experimented upon sickened and many of them died; and in their
blood he found the malarial parasite.
We now understand why the flagellated body is developed outside the
human host: because its function lies outside the human host. We now
understand why the flagella break away and enter the granular sphere:
they impregnate it and start it on the road of development. We now
understand why MacCallum’s vermicule is beaked and endowed with powers
of locomotion and penetration: that it may approach and penetrate the
stomach of the mosquito. And we now know why the sporozooites, the
‘germinal rods,’ enter the mosquito’s salivary gland: that they may be
injected into vertebrate issue and so pass the parasite from vertebrate
to vertebrate.
This is one of those fairy tales of science which people are inclined
to doubt, but any one who has worked at the subject and taken the
trouble to go through the long series of preparations which have been
sent home from India can not for a moment have the slightest doubt
that what Ross stated was absolutely true, and that not only for bird
but for human malaria. So soon as the idea got abroad that the key to
the way in which the malarial parasite is propagated had been found
the Italians immediately set to work with renewed vigor and with the
utmost skill. Almost at once they demonstrated that what happened in
the case of Ross’s sparrows happened also with the human subject: that
the appropriate species of mosquito fed upon the human malarial subject
and subsequently allowed to feed upon a non-malarial subject conveyed
the malarial parasite and malarial disease, and that the appropriate
species of mosquito belonged to the genus anopheles. There can not be
the slightest doubt that the mosquito acts the part of transmitting
agent as well as definitive host of the malarial parasite.
This is a piece of knowledge of the utmost importance to mankind, for
we know that malarial disease in tropical countries--which, after
all, in the future will be the most important parts of the world,
seeing that they can produce more food than temperate countries and
can therefore support a larger population--causes more deaths and more
disposition to death by inducing cachectic states predisposing to other
affections than all the other parasites affecting mankind put together.
We know now in what way this parasite is acquired. Depend upon it,
in time, in virtue of this knowledge, we will get enormous power
over the disease and sooner or later we will be able to prevent the
infection of man by the parasite. It is only a question of study and
the application of the knowledge already acquired, only a question of
money and perseverance and a little ingenuity, and these results will
come. It may not be in ten years or twenty years, but sooner or later
the energies of a considerable portion of scientific mankind now being
expended in endeavoring to devise means for preventing the infection of
men with the malarial germ by the mosquito will bear valuable fruit.
You can readily understand that it is of great importance to be able
to recognize the special species of mosquito which convey malaria.
The effective species as regards human malaria belong to the genus
anopheles; species of the genus culex are effective in the case of
sparrow malaria. Fortunately, these two genera are easily recognized
even by the amateur zoölogist. If you find a mosquito clinging to
the wall or other surface you can tell which genus it belongs to by
its posture. If the body is stuck out nearly at right angles to the
surface on which the insect is resting, it is an anopheles. If the body
is almost parallel to the surface, it is a culex. There is another
test which is easily applied if you have a pocket lens; in culex the
two organs known as palpi are rudimentary and very short; whereas
in anopheles those organs are almost as long as the proboscis. It
should be remembered that the male mosquito is not a blood-sucker and
therefore is not dangerous. It is the female anopheles which transmits
the disease. The mosquito larvæ inhabit stagnant or slow-running water.
If a mosquito larva be found with its head downwards, the body hanging
at right angles to the surface of the water, it is a culex; if the body
lies parallel to the surface of the water, it is an anopheles. There
are other points of difference with which I need not now trouble you;
those referred to suffice for diagnosis between the innocuous and the
dangerous mosquitoes.
The facts regarding the malaria parasite which I have described are
of great importance for many reasons. First, because they help us to
understand the pathology and etiology of malaria. Secondly, they help
us in diagnosis. Thirdly, our knowledge of the parasite is invaluable
in directing treatment. Lastly, a knowledge of the life-history of the
malarial parasite is of extreme value for the prevention of malarial
disease, for could we by mechanical or other arrangements prevent
the mosquito attacking the human body, we could prevent the malarial
parasites from entering the human body; or if we could abolish the
mosquito by drainage or other means from a country, then we might be
sure that we would abolish the malaria of that country also.
Attempts are being made to solve these practical problems. At the
present moment such attempts are being actively made in Rome by
Professor Celli and elsewhere by others. I have no doubt that in the
course of a few years we shall get some very valuable results in
this direction and that, thanks to this new-born knowledge about the
malarial parasites, better times are rapidly approaching for malarial
countries.
NEW SOURCES OF LIGHT AND OF RÖNTGEN RAYS.
BY HENRY CARRINGTON BOLTON, PH. D.
Among the general laws of physical science, none seems more firmly
established than that of the conservation and correlation of energy;
according to this the various forms of energy that constitute the
domain of experimental physics, heat, light, electricity, magnetism
and chemical action, have reciprocal dependence and “can not originate
otherwise than by devolution from some preëxisting force,” or rather
energy. That motion is convertible into heat, heat into light and both
the former into electricity are phenomena familiar to every one who
uses incandescent bulbs or rides in a trolley, and we do not usually
recognize any production of light unaccompanied by heat. True, the
little fire-fly is possessed of a mysterious power that enables it
to emit light without enough heat to affect Langley’s most sensitive
bolometer, but the eminent Secretary of the Smithsonian has to admit
that the “cheapest form of light” is produced by “processes of nature
of which we know nothing.” This little understood property called
phosphorescence is shared by many living organisms, both animal and
vegetable, as well as by substances of the mineral kingdom; to the
former belong coelenterates, mollusks, crustacea, fishes and insects,
and decaying wood, certain mushrooms, etc.; to the latter the Bologna
stone, so-called, and the commercial article called ‘Balmain’s paint.’
In the case of the mineral substances, barium or calcium sulfids and
the like, the light-giving power is not an innate property, but is
set in operation by exposure to the energy of sunlight, the light of
burning magnesium or to some other source of actinism; moreover, the
power thus acquired by insolation is a fugitive one, the substances
exercising it after three or four hours become ‘dead’ and lose their
activity. Excepting then these living beings and these phosphorescent
bodies, light as commonly known to us is always correlated with heat;
within the last four years, however, discoveries have been made in
France that seem to modify the position taken by philosophers and to
necessitate new views concerning the manifestations of that energy with
which the universe is endowed. A group of French savants have found
mineral substances that apparently give out light perpetually without
any exciting cause, realizing the dream of the alchemists--a perpetual
lamp consuming no oil. These substances also emit rays having the
penetrating properties of X-rays, other rays affecting a photographic
plate, and fourthly, rays causing air to become a conductor of
electricity. The history of these discoveries can be briefly given.
Röntgen’s discovery of the rays that pass through metals and solids
opaque to light was made in 1895, and in the following year, Becquerel,
a distinguished French academician, discovered that salts of the metal
uranium (substances that had long been used in coloring china and
glass) emit invisible radiations capable of discharging electrified
bodies and of producing skiagraphic images on sensitive plates; he
found that potassio-uranic sulfate emits rays that pass through black
paper and give photographic impressions in the same way as Röntgen
rays. This property is not limited to the brilliantly fluorescent
uranic salts, but is shared by the non-fluorescent uranous salts,
and is exhibited by compounds whether phosphorescent or not, whether
crystalline, melted or in solution, as well as by the metal itself. The
permanence of this activity is amazing, substances kept in a double
leaden box more than three years continuing to exert the power.
Shortly after the announcement by Becquerel, experimenters found that
other substances have the power of emitting ‘Becquerel Rays,’ such
as calcium and zinc sulfids and compounds of thorium. In 1898 Mme.
Sklodowska Curie, working in the laboratory of the Municipal School of
Industrial Physics and Chemistry in Paris, devised a special apparatus
for measuring the electrical conductivity of the air when under the
influence of ‘radio-active bodies,’ and by its means studied the
behavior of pitchblende (uraninite), and of other uranium minerals;
finding that some specimens of pitchblende had three times as much
energy as uranium itself, she came to the conclusion that the peculiar
property is due to some unknown body contained in the minerals and not
to uranium. Examining the mineral with the aid of her husband, the two
found a substance analogous to bismuth, four thousand times stronger
than uranium, which was named ‘Polonium,’ in honor of the native land
of Mme. Curie. In December of the same year, the lady received the
Gegner prize of 4,000 francs awarded by the Academy of Sciences, as
a substantial appreciation of her discovery, and later in the same
month Mme. and M. Curie announced that they had found a second body in
pitchblende, which they named ‘Radium.’ More recently, M. Debierne,
working under the auspices of Mme. Curie, has discovered a third
body, which he calls ‘Actinium,’ an unfortunate appellation because
‘actinium’ has already been used for an element announced by Dr.
Phipson and since discarded.
These three ‘radio-active’ substances do not possess identical
properties; their rays are unequally absorbed and are differently
affected in a magnetic field; moreover radium emits visible rays, while
polonium does not. Nor have they the same chemical affinities; polonium
belongs to the bismuth group, radium to the barium and actinium to the
titanium series. They have not been separated perfectly from their
analogues, and consequently their chemical properties and the actual
intensity of their physical activities is very imperfectly known. The
difficulties of securing even small quantities of crude materials
are enormous; Fritz Giesel obtained from one thousand kilograms of
raw material only fifteen grams of active compounds, and Mme. Curie,
operating on half a ton of the residues of uranium from a chemical
manufactory, got about two kilograms of barium chloride rich in radium,
but the percentage of active substances in these mixtures is unknown.
Radium is spontaneously luminous, and all the bodies emit rays that
excite phosphorescence in gems, fluorite and other minerals; they
communicate radiant energy to inactive substances, and they exert
chemical action, transforming oxygen into ozone and producing changes
in the color of glass and of barium platino-cyanid.
Through the enterprise and liberality of the Smithsonian Institution,
and by the courtesy of Professor Langley, I have enjoyed the
opportunity of studying small specimens of these rare and costly
substances; they comprised ten grams of ‘radio-active substance’
prepared by a manufacturing chemist of Germany and smaller quantities
of ‘radium’ and of ‘polonium’ from Paris. On removing the wrappings
of the German specimens in a dark room, they were seen to emit
greenish-white light that gave to the enveloping papers a peculiar
glow, similar to the fluorescence produced by Röntgen rays. Simple
tests of the radium showed that it gave the usual reactions of barium;
on boiling it with water it lost its luminosity, but on heating to dull
redness this property returned in the dark. It also caused a barium
platino-cyanid screen to fluoresce.
Experiments to test the actinic power of these bodies gave interesting
results; on exposing sections of photographic plates, at distances of
five inches, from two to twelve minutes, bands were obtained varying
in intensity with the duration of action. By exposing sensitive plates
behind negatives to the radiant materials from two to three hours,
excellent transparencies were secured; on substituting Eastman’s
bromide paper good prints were obtained.
The penetrating power of the rays emitted permits the production
of skiagraphs; the plates were enveloped in Carbutt’s black paper
(impermeable to light), and on them were laid pieces of tinfoil cut
in openwork pattern; after one hour’s exposure negatives were secured
plainly showing the pattern. Analogous experiments were carried on with
the specimens from Paris, but they were only one fifth as strong in
effects; that labelled ‘polonium sub-nitrate’ had positively no action
on the plates used.
The primary source of the energy manifested by these extraordinary
substances has greatly puzzled physicists, and as yet remains a
mystery. Mme. Curie, speculating on the matter, conjectured that all
space is continually traversed by rays analogous to Röntgen rays, but
far more penetrating, and not capable of being absorbed by certain
elements of high atomic weight, such as uranium and thorium. Becquerel,
reflecting on the marvellous spontaneous emission of light, said: “If
it can be proved that the luminosity causes no loss of energy, the
state of the uranium is like that of a magnet which has been produced
by an expenditure of energy and retains it indefinitely, maintaining
around it a field in which transformation of energy can be effected;
but the photographic reductions and the excitation of phosphorescence
require an expenditure of energy, of which the source can only be in
the radio-active substances.” Somewhat later, Becquerel hazarded the
opinion that the radiation is composed at least in part of cathodic
rays; but these have been proved to be material, hence the induced
activity must be caused by material particles impinging upon the
substances excited. This materialistic theory seems to be confirmed by
the results of ingenious experiments made by Mme. and M. Curie; they
placed a sensitive plate beneath a salt of radium supported on a slab
of lead, in the vicinity of an electro-magnet. Under these conditions,
when the current was passing, the rays emitted were bent in curved
lines upon the sensitive plate, making impressions.
It may be objected, says a French writer, that the materialistic theory
requires us to admit actual loss of particles of matter, nevertheless
the charges are so feeble that the most intense radiation yet observed
would require millions of years for the removal of one milligram of
substance.
While writing these lines, we have news of experiments that seem to
throw doubt on the elementary character of these radio-active bodies;
Bela von Lengyel, of Budapest, claims to have prepared the so-called
‘radium’ synthetically. By fusing with the heat of electricity uranium
nitrate mixed with a small percentage of barium nitrate, and treating
the mass with acids, he obtained a substance that gives out actinic
rays, Röntgen rays, excites platino-cyanid screens and causes air to
conduct electricity; in short, the Hungarian chemist gets material
possessing all the properties characteristic of the ‘element’ announced
by Mme. Curie.
Admitting that radio-active bodies can be manufactured to order, are we
any nearer explaining their mysterious powers?
Speculations as to the future history and applications of these
wonder-working bodies press upon even the dullest imagination; if a
few grams of earth-born material, containing only a small percentage
of the active body, emit light enough to affect the human eye and a
photographic plate, as well as rays that penetrate with X-ray power,
what degree of luminosity, of actinism and of Röntgenism (if the
term may be allowed), is to be expected from an hundred weight of
the quintessence of energy purified from interfering matter? And to
what uses is this light-generating material to be applied? Are our
bicycles to be lighted with discs of radium in tiny lanterns? Are these
substances to give us the ‘cheapest form of light?’ Are we about to
realize the chimerical dream of the alchemists?
Seriously, in what direction is profound study of these substances
going to lead us? Will it not greatly extend our knowledge of physical
manifestations of energy and their correlation? In what corner of
the globe will be found the cheap and convenient supply of the raw
material yielding the radio-active bodies? Will not chemists be obliged
to re-examine much known material by laboratory methods conducted in
the dark? Many of us have worked up pounds of pitchblende to extract
the uranium oxids, and in so doing have poured down the waste-pipe or
thrown into the dust-bin the more interesting and precious bodies.
Whatever the future may bring, scientists are deeply indebted to
Becquerel and to Mme. and M. Curie for placing in their hands new
methods of research and for furnishing a novel basis for speculation
destined to yield abundant fruits.
DISCUSSION AND CORRESPONDENCE.
_WASHINGTON AS AN EXPLORER AND SURVEYOR._