(Original.)]
There remain for consideration the Southern and Western forms--_Rasatus
thoracicus_ and _R. biguttatus_, and _Conorhinus sanguisugus_.
The two-spotted corsair, as _Rasatus biguttatus_ is popularly termed,
is said by Riley to be found frequently in houses in the Southern
States, and to prey upon bedbugs. Lintner, referring to the fact that
it preys upon bedbugs, says: "It evidently delights in human blood, but
prefers taking it at second hand." Dr. A. Davidson, formerly of Los
Angeles, Cal., in an important paper entitled So-called Spider Bites
and their Treatment, published in the Therapeutic Gazette of February
15, 1897, arrives at the conclusion that almost all of the so-called
spider bites met with in southern California are produced by no spider
at all, but by _Rasatus biguttatus_. The symptoms which he describes
are as follows: "Next day the injured part shows a local cellulitis,
with a central dark spot; around this spot there frequently appears
a bullous vesicle about the size of a ten-cent piece, and filled with
a dark grumous fluid; a small ulcer forms underneath the vesicle, the
necrotic area being generally limited to the central part, while the
surrounding tissues are more or less swollen and somewhat painful. In
a few days, with rest and proper care, the swelling subsides, and in
a week all traces of the cellulitis are usually gone. In some of the
cases no vesicle forms at the point of injury, the formation probably
depending on the constitutional vitality of the individual or the
amount of poison introduced." The explanation of the severity of the
wound suggested by Dr. Davidson, and in which the writer fully concurs
with him, is not that the insect introduces any specific poison of
its own, but that the poison introduced is probably accidental and
contains the ordinary putrefactive germs which may adhere to its
proboscis. Dr. Davidson's treatment was corrosive sublimate--1 to 500
or 1 to 1,000--locally applied to the wound, keeping the necrotic part
bathed in the solution. The results have in all cases been favorable.
Uhler gives the distribution of _R. biguttatus_ as Arizona, Texas,
Panama, Pará, Cuba, Louisiana, West Virginia, and California. After a
careful study of the material in the United States National Museum,
Mr. Heidemann has decided that the specimens of _Rasatus_ from the
southeastern part of the country are in reality Say's _R. biguttatus_,
while those from the Southwestern States belong to a distinct species
answering more fully, with slight exceptions, to the description of
Stal's _Rasatus thoracicus_. The writer has recently received a large
series of _R. thoracicus_ from Mr. H. Brown, of Tucson, Arizona, and
had a disagreeable experience with the same species in April, 1898, at
San José de Guaymas, in the State of Sonora, Mexico. He had not seen
the insect alive before, and was sitting at the supper table with his
host--a ranchero of cosmopolitan language. One of the bugs, attracted
by the light, flew in with a buzz and flopped down on the table. The
writer's entomological instinct led him to reach out for it, and was
warned by his host in the remarkable sentence comprising words derived
from three distinct languages: "Guardez, guardez! Zat animalito sting
like ze dev!" But it was too late; the writer had been stung on the
forefinger, with painful results. Fortunately, however, the insect's
beak must have been clean, and no great swelling or long inconvenience
ensued.
Perhaps the best known of any of the species mentioned in our list is
the blood-sucking cone-nose (_Conorhinus sanguisugus_). This ferocious
insect belongs to a genus which has several representatives in the
United States, all, however, confined to the South or West. _C.
rubro-fasciatus_ and _C. variegatus_, as well as _C. sanguisugus_,
are given the general geographical distribution of "Southern States."
_C. dimidiatus_ and _C. maculipennis_ are Mexican forms, while _C.
gerstaeckeri_ occurs in the Western States. The more recently described
species, _C. protractus_ Uhl., has been taken at Los Angeles, Cal.;
Dragoon, Ariz.; and Salt Lake City, Utah. All of these insects are
blood-suckers, and do not hesitate to attack animals. Le Conte, in his
original description of _C. sanguisugus_,[5] adds a most significant
paragraph or two which, as it has not been quoted of late, will be
especially appropriate here: "This insect, equally with the former"
(see above), "inflicts a most painful wound. It is remarkable also
for sucking the blood of mammals, particularly of children. I have
known its bite followed by very serious consequences, the patient not
recovering from its effects for nearly a year. The many relations which
we have of spider bites frequently proving fatal have no doubt arisen
from the stings of these insects or others of the same genera. When
the disease called spider bite is not an anthrax or carbuncle it is
undoubtedly occasioned by the bite of an insect--by no means however,
of a spider. Among the many species of _Araneidæ_ which we have in the
United States I have never seen one capable of inflicting the slightest
wound. Ignorant persons may easily mistake a _Cimex_ for a spider. I
have known a physician who sent to me the fragments of a large ant,
which he supposed was a spider, that came out of his grandchild's
head." The fact that Le Conte was himself a physician, having graduated
from the College of Physicians and Surgeons in 1846, thus having been
nine years in practice at the time, renders this statement all the
more significant. The life history and habits of _C. sanguisugus_ have
been so well written up by my assistant, Mr. Marlatt, in Bulletin No.
4, New Series, of the Division of Entomology, United States Department
of Agriculture, that it is not necessary to enter upon them here.
The point made by Marlatt--that the constant and uniform character
of the symptoms in nearly all cases of bites by this insect indicate
that there is a specific poison connected with the bite--deserves
consideration, but there can be no doubt that the very serious results
which sometimes follow the bite are due to the introduction of
extraneous poison germs. The late Mr. J. B. Lembert, of Yosemite, Cal.,
noticed particularly that the species of _Conorhinus_ occurring upon
the Pacific coast is attracted by carrion. Professor Toumey, of Tucson,
Arizona, shows how a woman broke out all over the body and limbs with
red blotches and welts from a single sting on the shoulders. Specimens
of _C. sanguisugus_ received in July, 1899, from Mayersville, Miss.,
were accompanied by the statement--which is appropriate, in view of the
fact that the newspapers have insisted that the "kissing bug" prefers
the lip--that a friend of the writer was bitten on the lip, and that
the effect was a burning pain, intense itching, and much swelling,
lasting three or four days. The writer of the letter had been bitten
upon the leg and arm, and his brother was bitten upon both feet and
legs and on the arm, the symptoms being the same in all cases.
[5] Proceedings of the Academy of Natural Sciences of Philadelphia,
vol. vii, p. 404 1854-'55.
More need hardly be said specifically concerning these biting bugs.
The writer's conclusions are that a puncture by any one of them may
be and frequently has been mistaken for a spider bite, and that
nearly all reported spider-bite cases have had in reality this cause,
that the so-called "kissing-bug" scare has been based upon certain
undoubted cases of the bite of one or the other of them, but that other
bites, including mosquitoes, with hysterical and nervous symptoms
produced by the newspaper accounts, have aided in the general alarm.
The case of Miss Larson, who died in August, 1898, as the result of
a mosquito bite, at Mystic, Conn., is an instance which goes to show
that no mysterious new insect need be looked for to explain occasional
remarkable cases. One good result of the "kissing-bug" excitement will
prove in the end to be that it will have relieved spiders from much
unnecessary discredit.
THE MOSQUITO THEORY OF MALARIA.[6]
BY MAJOR RONALD ROSS.
I have the honor to address you, on completion of my term of special
duty for the investigation of malaria, on the subject of the practical
results as regard the prevention of the disease which may be expected
to arise from my researches; and I trust that this letter may be
submitted to the Government if the director general thinks fit.
[6] A report, published in Nature, from Major Ronald Ross to the
Secretary to the Director General, Indian Medical Service, Simla. Dated
Calcutta, February 16, 1899.
It has been shown in my reports to you that the parasites of malaria
pass a stage of their existence in certain species of mosquitoes, by
the bites of which they are inoculated into the blood of healthy men
and birds. These observations have solved the problem--previously
thought insolvable--of the mode of life of these parasites in external
Nature.
My results have been accepted by Dr. Laveran, the discoverer of the
parasites of malaria; by Dr. Manson, who elaborated the mosquito
theory of malaria; by Dr. Nuttall, of the Hygienic Institute of
Berlin, who has made a special study of the relations between insects
and disease; and, I understand, by M. Metchnikoff, Director of the
Laboratory of the Pasteur Institute in Paris. Lately, moreover, Dr. C.
W. Daniels, of the Malaria Commission, who has been sent to study with
me in Calcutta, has confirmed my observations in a special report to
the Royal Society; while, lastly, Professor Grassi and Drs. Bignami
and Bastianelli, of Rome, have been able, after receiving specimens
and copies of my reports from me, to repeat my experiments in detail,
and to follow two of the parasites of human malaria through all their
stages in a species of mosquito called the _Anopheles claviger_.
It may therefore be finally accepted as a fact that malaria is
communicated by the bites of some species of mosquito; and, to judge
from the general laws governing the development of parasitic animals,
such as the parasites of malaria, this is very probably the only way in
which infection is acquired, in which opinion several distinguished men
of science concur with me.
In considering this statement it is necessary to remember that it does
not refer to the mere recurrences of fever to which people previously
infected are often subject as the result of chill, fatigue, and so on.
When I say that malaria is communicated by the bites of mosquitoes, I
allude only to the original infection.
It is also necessary to guard against assertions to the effect that
malaria is prevalent where mosquitoes and gnats do not exist. In my
experience, when the facts come to be inquired into, such assertions
are found to be untrue. Scientific research has now yielded so absolute
a proof of the mosquito theory of malaria that hearsay evidence opposed
to it can no longer carry any weight.
Hence it follows that, in order to eliminate malaria wholly or partly
from a given locality, it is necessary only to exterminate the various
species of insect which carry the infection. This will certainly
remove the malaria to a large extent, and will almost certainly remove
it altogether. It remains only to consider whether such a measure is
practicable.
Theoretically the extermination of mosquitoes is a very simple matter.
These insects are always hatched from aquatic larvæ or grubs which can
live only in small stagnant collections of water, such as pots and tubs
of water, garden cisterns, wells, ditches and drains, small ponds,
half-dried water courses, and temporary pools of rain-water. So far as
I have yet observed, the larvæ are seldom to be found in larger bodies
of water, such as tanks, rice fields, streams, and rivers and lakes,
because in such places they are devoured by minnows and other small
fish. Nor have I ever seen any evidence in favor of the popular view
that they breed in damp grass, dead leaves, and so on.
Hence, in order to get rid of these insects from a locality, it will
suffice to empty out or drain away, or treat with certain chemicals,
the small collections of water in which their larvæ must pass their
existence.
But the practicability of this will depend on
circumstances--especially, I think, on the species of mosquito with
which we wish to deal. In my experience, different species select
different habitations for their larvæ. Thus the common "brindled
mosquitoes" breed almost entirely in pots and tubs of water; the
common "gray mosquitoes" only in cisterns, ditches, and drains; while
the rarer "spotted-winged mosquitoes" seem to choose only shallow
rain-water puddles and ponds too large to dry up under a week or more,
and too small or too foul and stagnant for minnows.
Hence the larvæ of the first two varieties are found in large numbers
round almost all human dwellings in India; and, because their breeding
grounds--namely, vessels of water, drains, and wells--are so numerous
and are so frequently contained in private tenements, it will be almost
impossible to exterminate them on a large scale.
On the other hand, spotted-winged mosquitoes are generally much
more rare than the other two varieties. They do not appear to breed
in wells, cisterns, and vessels of water, and therefore have no
special connection with human habitations. In fact, it is usually
a matter of some difficulty to obtain their larvæ. Small pools of
any permanence--such as they require--are not common in most parts
of India, except during the rains, and then pools of this kind are
generally full of minnows which make short work of any mosquito
larvæ they may find. In other words, the breeding grounds of the
spotted-winged varieties seem to be so isolated and small that I
think it may be possible to exterminate this species under certain
circumstances.
The importance of these observations will be apparent when I add
that hitherto the parasites of human malaria have been found only in
spotted-winged mosquitoes--namely, in two species of them in India and
in one species in Italy. As a result of very numerous experiments I
think that the common brindled and gray mosquitoes are quite innocuous
as regards human malaria--a fortunate circumstance for the human race
in the tropics; and Professor Grassi seems to have come to the same
conclusion as the result of his inquiries in Italy.
But I wish to be understood as writing with all due caution on these
points. Up to the present our knowledge, both as regards the habits
of the various species of mosquito and as regards the capacity of each
for carrying malaria, is not complete. All I can now say is that if
my anticipations be realized--if it be found that the malaria-bearing
species of mosquito multiply only in small isolated collections of
water which can easily be dissipated--we shall possess a simple mode of
eliminating malaria from certain localities.
I limit this statement to certain localities only, because it is
obvious that where the breeding pools are very numerous, as in
water-logged country, or where the inhabitants are not sufficiently
advanced to take the necessary precautions, we can scarcely expect the
recent observations to be of much use--at least for some years to come.
And this limitation must, I fear, exclude most of the rural areas in
India.
Where, however, the breeding pools are not very numerous, and where
there is anything approaching a competent sanitary establishment, we
may, I think, hope to reap the benefit of these discoveries. And this
should apply to the most crowded areas, such as those of cities, towns
and cantonments, and also to tea, coffee, and indigo estates, and
perhaps to military camps.
For instance, malaria causes an enormous amount of sickness among the
poor in most Indian cities. Here the common species of mosquitoes breed
in the precincts of almost all the houses, and can therefore scarcely
be exterminated; but pools suitable for the spotted-winged varieties
are comparatively scarce, being found only on vacant areas, ill-kept
gardens, or beside roads in very exceptional positions where they can
neither dry up quickly nor contain fish. Thus a single small puddle
may supply the dangerous mosquitoes to several square miles containing
a crowded population: if this be detected and drained off--which will
generally cost only a very few rupees--we may expect malaria to vanish
from that particular area.
The same considerations will apply to military cantonments and estates
under cultivation. In many such malaria causes the bulk of the
sickness, and may often, I think, originate from two or three small
puddles of a few square yards in size. Thus in a malarious part of
the cantonment of Secunderabad I found the larvæ of spotted-winged
mosquitoes only after a long search in a single little pool which could
be filled up with a few cart-loads of town rubbish.
In making these suggestions I do not wish to excite hopes which may
ultimately prove to have been unfounded. We do not yet know all the
dangerous species of mosquito, nor do we even possess an exhaustive
knowledge of the haunts and habits of any one variety. I wish merely
to indicate what, so far as I can see at present, may become a very
simple means of eradicating malaria.
One thing may be said for certain. Where previously we have been unable
to point out the exact origin of the malaria in a locality, and have
thought that it rises from the soil generally, we now hope for much
more precise knowledge regarding its source; and it will be contrary to
experience if human ingenuity does not finally succeed in turning such
information to practical account.
More than this, if the distinguishing characteristics of the
malaria-bearing mosquitoes are sufficiently marked (if, for instance,
they all have spotted wings), people forced to live or travel in
malarious districts will ultimately come to recognize them and to take
precautions against being bitten by them.
Before practical results can be reasonably looked for, however, we must
find precisely--
(_a_) What species of Indian mosquitoes do and do not carry human
malaria.
(_b_) What are the habits of the dangerous varieties.
I hope, therefore, that I may be permitted to urge the desirability of
carrying out this research. It will no longer present any scientific
difficulties, as only the methods already successfully adopted will be
required. The results obtained will be quite unequivocal and definite.
But the inquiry should be exhaustive. It will not suffice to
distinguish merely one or two malaria-bearing species of mosquito in
one or two localities; we should learn to know all of them in all parts
of the country.
The investigation will be abbreviated if the dangerous species be found
to belong only to one class of mosquito, as I think is likely; and the
researches which are now being energetically entered upon in Germany,
Italy, America, and Africa will assist any which may be undertaken in
India, though there is reason for thinking that the malaria-bearing
species differ in various countries.
As each species is detected it will be possible to attempt measures at
once for its extermination in given localities as an experiment.
I regret that, owing to my work connected with _kala-azar_, I have not
been able to advance this branch of knowledge as much during my term
of special duty as I had hoped to do; but I think that the solution of
the malaria problem which has been obtained during this period will
ultimately yield results of practical importance.
FOOD POISONING.
BY VICTOR C. VAUGHAN,
PROFESSOR OF HYGIENE IN THE UNIVERSITY OF MICHIGAN.
Within the past fifteen or twenty years cases of poisoning with foods
of various kinds have apparently become quite numerous. This increase
in the number of instances of this kind has been both apparent and
real. In the first place, it is only within recent years that it has
been recognized that foods ordinarily harmless may become most powerful
poisons. In the second place, the more extensive use of preserved
foods of various kinds has led to an actual increase in the number of
outbreaks of food poisoning.
The harmful effects of foods may be due to any of the following causes:
1. Certain poisonous fungi may infect grains. This is the cause of
epidemics of poisoning with ergotized bread, which formerly prevailed
during certain seasons throughout the greater part of continental
Europe, but which are now practically limited to southern Russia and
Spain. In this country ergotism is practically unknown, except as a
result of the criminal use of the drug ergot. However, a few herds of
cattle in Kansas and Nebraska have been quite extensively affected with
this disease.
2. Plants and animals may feed upon substances that are not harmful
to them, but which may seriously affect man on account of his greater
susceptibility. It is a well-known fact that hogs may eat large
quantities of arsenic or antimony without harm to themselves, and thus
render their flesh unfit for food for man. It is believed that birds
that feed upon the mountain laurel furnish a food poisonous to man.
3. During periods of the physiological activity of certain glands
in some of the lower animals the flesh becomes harmful to man. Some
species of fish are poisonous during the spawning season.
4. Both animal and vegetable foods may become infected with the
specific germs of disease and serve as the carriers of the infection to
man. Instances of the distribution of typhoid fever by the milkman are
illustrations of this.
5. Animals may be infected with specific diseases, which may be
transmitted to man in the meat or milk. This is one of the means by
which tuberculosis is spread.
6. Certain nonspecific, poison-producing germs may find their way into
foods of various kinds, and may by their growth produce chemical
poisons either before or after the food has been eaten. This is the
most common form of food poisoning known in this country.
We will briefly discuss some foods most likely to prove harmful to man.
MUSSEL POISONING.--It has long been known that this bivalve is
occasionally poisonous. Three forms of mussel poisoning are recognized.
The first, known as _Mytilotoxismus gastricus_, is accompanied by
symptoms practically identical with those of cholera morbus. At first
there is nausea, followed by vomiting, which may continue for hours.
In severe cases the walls of the stomach are so seriously altered that
the vomited matter contains considerable quantities of blood. Vomiting
is usually accompanied by severe and painful purging. The heart may be
markedly affected, and death may result from failure of this organ.
Examination after death from this cause shows the stomach and small
intestines to be highly inflamed.
The second form of mussel poisoning is known as _Mytilotoxismus
exanthematicus_ on account of visible changes in the skin. At first
there is a sensation of heat, usually beginning in the eyelids, then
spreading to the face, and finally extending over the whole body.
This sensation is followed by an eruption, which is accompanied by
intolerable itching. In severe cases the breathing becomes labored, the
face grows livid, consciousness is lost, and death may result within
two or three days.