the mosquito serves as the intermediate host of the parasite of yellow fever.

One of the two cases in which positive results were obtained in this preliminary work was a member of the board, Dr. Lazear, and in this case the result was fatal. The cause of science has had many martyrs, but this was one of the saddest, and was undoubtedly one of the greatest losses to humanity. Dr. Lazear was a young man of great ability, admirably trained, whose work, as Dr. Reed says, was characterized by "a manly and fearless devotion to duty such as I have never seen equaled." He "seemed absolutely tireless and quite oblivious of self. Filled with an earnest enthusiasm for the advancement of his profession and for the cause of science, he let no opportunity pass unimproved. Although the evening might find him discouraged over the difficult problem at hand, with the morning's return he again took up the task, full of eagerness and hope."

It is not surprising, therefore, that when the board resumed its work late in November, 1900, and established an experiment station one mile from Quemado, Cuba, they should name it, in honor of their comrade, "Camp Lazear." Here Camp Lazear." Here were built the two experiment houses which

have become famous. One of them was termed the "infected-mosquito building," and the other the "infected-clothing building." The former was screened and well ventilated, while the other was screened and poorly ventilated. In the former patients were bitten by infected mosquitos; in the latter no mosquitos were admitted, but the persons submitting themselves to the experiment slept with soiled bedding and clothing direct from the yellow-fever hospitals. Briefly stated, in thirteen cases where non-immunes were bitten by mosquitos which had bitten a yellow-fever patient at least twelve days previously, ten contracted the disease, while in the infected-clothing house, although volunteers had slept there for many nights, no single case of yellow fever was contracted.

The experiments were conducted with. such care that no criticism is possible. Criticism was invited from resident physicians in Havana and from medical visitors, but none was made. The results were perfect, and were absolutely conclusive.

The men who submitted themselves to the experiment were hospital attendants, American soldiers, and Spanish immigrants, none of whom had ever had yellow fever. The heroism exhibited by these persons, and especially by the Americans, is beyond

praise. Speaking of Kissinger, a young Ohio soldier who was the first person bitten by infected mosquitos, Dr. Reed says: "I cannot let this opportunity pass without expressing my admiration of the conduct of this young Ohio soldier, who volunteered for this experiment, as he expressed it, 'solely in the interest of humanity and the cause of science,' and with the only proviso that he should receive no pecuniary reward. In my opinion, this exhibition of moral courage has never been surpassed in the annals of the army of the United States." The next three cases were Spaniards, and all of these first four contracted the fever. After that no more Spanish patients could be secured. They had allowed themselves to be bitten largely through incredulity and for a money reward. After the fever appeared, they lost their interest in the cause of science, and preferred safety to money. Other Americans, however, immediately volunteered, and, praising their courage in the highest degree, we must not fail to point out here that the inspiration was derived from Dr. Reed himself. Nothing but the most absolute confidence in this remarkable man could have gained him his subjects, and the confidence was justified, since this series of experiments, the result of which has already been of inestimable value to humanity, was accomplished without the loss of a single human life.

One must be struck with the modesty of the men composing the commission when, without a single symptom of selflaudation, the results of this remarkable experimental work, destined to revolu

the simple title, "The Etiology of Yellow Fever: An Additional Note"! (The italics are the writer's.)

It was after the publication of the "Preliminary Note" that the comment quoted in our introduction was made by the " British Medical Journal." After the publication of the "Additional Note," however, the medical profession accepted the results and conclusion of the commission with virtual unanimity. During this work, and for months subsequently, continued investigations were carried on by members of the commission for the causative microorganism of the disease, but it has not yet been found. It was discovered that the disease could be conveyed not only by the bite of the mosquito, but by the injection of the blood serum of a yellow-fever patient into the system of a non-immune. It was further discovered that this blood serum could be filtered through porcelain and yet retain its power to convey the disease. It seems certain, therefore, that the cause is either some micro-organism so excessively small as to pass through porcelain, so excessively small, therefore, as to fail to reveal itself to the highest powers

of the microscope,

or else that the disease is conveyed by some toxin. Experiments were then made by submitting the serum to various degrees of heat, and it was found that its toxicity was destroyed by a comparatively low temperature-one low, in fact, to have any effect upon any toxin; and the conclusion is almost unavoidable that the cause of yellow fever is a micro-organism in the blood which is

too

size.

It would be very strange if so great a discovery as this had not its objectors. At first, and before the papers of the commission had been widely read, there were physicians who announced total disbelief; but these were soon silenced. Since then, and especially in the Southern United States, there have been a number of physicians who, while admitting that the disease is carried by mosquitos, still contend that there probably is some other means of transmission. These physicians, and no less a person than Dr. Souchon, president

ments were carried on at Las Animas Hospital by the director of the hospital, Surgeon John W. Ross of the United States navy, and these experiments were made with the purpose of setting at rest the still-adhered-to theory of the transmission of the disease by fomites or clothing or other articles which had come into contact with yellow-fever patients. Certain rooms in the hospital were made mosquitoproof, and numerous bundles containing bedclothes and bedding which had recently been used in the sick-rooms and on the

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of the Louisiana Board of Health, who is a leader, hold that there are many recorded outbreaks where the mosquito agency is improbable or impossible, and they hold that no great variations in quarantine methods must be introduced until the matter is set entirely at rest. Additional experiments were carried on in 1901 by the Havana Board of Health, under the wellknown yellow-fever expert Dr. Juan Guiteras, formerly of the University of Pennsylvania, at Las Animas Hospital. In a number of cases the disease was experimentally conveyed by the bites of infected mosquitos, but here, unfortunately, several lives were lost. Later in the autumn and winter of 1901 very careful experi

persons of patients ill with yellow fever were placed in these rooms; eight men recently arrived on the island (five Spanish, two Italian, and one English) were taken as subjects for experimentation. They were placed under observation for seven days, and then transferred to the experiment room, where they were kept for seven days. They were then kept under observation for seven days longer, with the result that all emerged from the experiment in good health.

Quite recently experiments of a most careful kind have been made at São Paulo, Brazil, under the direction of Dr. Adolpho Lutz, director of the Bacteriological Institution of the State of São Paulo. These

experiments were extremely interesting, since the mosquitos chosen were brought from uninfected places, allowed to bite a yellow-fever patient, sent to another uninfected place several hundred kilometers away, and allowed to bite non-immunes who had previously been quarantined and who submitted to the experiment of their own accord. Out of six cases there were three positive results, the fever appearing from seventy-five to eighty hours after the biting. All the patients recovered. These experiments were considered necessary, on account of the great local opposition to the so-called mosquito theory. But now the question is considered solved, and the practical extermination of mosquitos has begun.

The beneficial effects of this great discovery were prophesied in the introduction. They are already evident in a marked degree in the city of Havana. For many months not one case of yellow fever was to be found in the city, although probably for one hundred and fifty years there had not been a day in which there were not cases of the disease. This condition is due to the fact that, first under the American administration and afterward under the Cuban Board of Health, the plain measures indicated by the discovery were put into effect. Before the discovery was made the health of the city improved under the active sanitary measures introduced and carried into effect by the untiring energy of General Ludlow. In spite of these measures, however, the fever was present. After the discovery, however, and under the very efficient direction of Major Gorgas, mosquito extermination began; breeding-places were abolished, and every yellow-fever patient was protected from the bites of mosquitos. The disease rapidly died out. With the new light brought to us by Reed and his colleagues, it is only necessary, when a case of yellow fever is discovered on board of a vessel entering a port, to see that the patient is thus protected, and there will be no opportunity for the disease to spread. In regions where the fever is endemic, all non-immunes keeping themselves protected from mosquito bites will undoubtedly remain free from the fever.

The distribution of the yellow-fever mosquito, Stegomyia fasciata, becomes at once of importance, for wherever the mos

quito abounds, an introduced case of fever becomes, without protection, a great danger. In general, this mosquito is found. in all parts of the world south of 380 north latitude and north of 380 south latitude. It is not, however, found at great elevations, and is mainly confined, in the United States, to that region of country known as the lower austral life-zone. This includes virtually all of the Gulf States, the Atlantic Coast States north to southern Virginia, the western portions of Kentucky and Tennessee, the southeastern corner of Missouri, and nearly all of Arkansas and the Indian Territory, southern New Mexico and Arizona, and southern California. It is known in Mexico and Central America, all of the West Indies, the low-lying portions of South America, Spain, southern Italy, parts of Africa, India, Farther India, Malay Archipelago, Australia, southern Japan, and Hawaii.

A peculiarity of the yellow-fever mosquito is that it bites by day as well as by night. To protect one's self from malaria, one has only to avoid mosquitos at night. The yellow-fever mosquito is known in the West Indies as the day mosquito. It is sometimes also called the striped mosquito. Its appearance is well shown in the accompanying figures, from which it will at once be recognized. It is essentially a house mosquito. It is not commonly found in the woods, but very abundantly in cities and about houses, where it breeds in the roof troughs, in water-tanks and -barrels, and in any chance receptacle of standing water. The eggs are laid singly in standing water, and will withstand desiccation. The water in which they are deposited may dry up entirely, but when, through rain, the receptacle again contains standing water, the eggs will hatch. The larvæ are much like those of other mosquitos; they are true airbreathers, and are readily killed by a kerosene film on the surface of the water.

One of the saddest aspects of this brilliant discovery is the death of the inspiring genius of the investigation, Dr. Walter Reed, who, with health impaired by his strenuous labors, died suddenly November 23, 1902, before he had fairly begun to reap the honors which were beginning to follow his monumental work. He will rank as one of the great benefactors of the human race.

1. DR. JUAN GUITERAS

The well-known yellow-fever expert, now connected with the sanitary service of the Cuban republic, and who conducted the first corroborative series of mosquito experiments in 1901 at Las Animas Hospital, Havana, Cuba.

2. DR. JOHN R. ROSS,
SURGEON, U. S. N.

He was in charge of Las Animas Hospital during 1901, and conducted a series of important corroborative experiments with fomites.

3. DR. JAMES CARROLL, U. S. V.

He was a member of the Army Commission and is the only survivor of the American members of the commission.

4. DR. CARLOS FINLAY He was the first to conduct experiments with the yellow-fever

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