WHEN the thoughtful historian gets far enough away from the nineteenth century to see it as a whole, no single feature will stand out with greater distinctness than the fulfilment of the prophecy of Descartes that we could be freed from an infinity of maladies both of body and mind if we had sufficient knowledge of their causes and of all the remedies with which nature has provided us. Sanitation takes its place among the great modern revolutions—political, social and intellectual. Great Britain deserves the credit for the first practical recognition of the maxim salus populi suprema lex. In the middle and latter part of the century a remarkable group of men, Southwood Smith, Chadwick, Budd, Murchison, Simon, Acland, Buchanan, J.W. Russell and Benjamin Ward Richardson, put practical sanitation on a scientific basis. Even before the full demonstration of the germ theory, they had grasped the conception that the battle had to be fought against a living contagion which found in poverty, filth and wretched homes the conditions for its existence. One terrible disease was practically wiped out in twenty-five years of hard work. It is difficult to realize that within the memory of men now living, typhus fever was one of the great scourges of our large cities, and broke out in terrible epidemics—the most fatal of all to the medical profession. In the severe epidemic in Ireland in the forties of the last century, one fifth of all the doctors in the island died of typhus. A better idea of the new crusade, made possible by new knowledge, is to be had from a consideration of certain diseases against which the fight is in active progress.

Nothing illustrates more clearly the interdependence of the sciences than the reciprocal impulse given to new researches in pathology and entomology by the discovery of the part played by insects in the transmission of disease. The flea, the louse, the bedbug, the house fly, the mosquito, the tick, have all within a few years taken their places as important transmitters of disease. The fly population may be taken as the sanitary index of a place. The discovery, too, that insects are porters of disease has led to a great extension of our knowledge of their life history. Early in the nineties, when Dr. Thayer and I were busy with the study of malaria in Baltimore, we began experiments on the possible transmission of the parasites, and a tramp, who had been a medical student, offered himself as a subject. Before we began, Dr. Thayer sought information as to the varieties of mosquitoes known in America, but sought in vain: there had at that time been no systematic study. The fundamental study which set us on the track was a demonstration by Patrick Manson,(3) in 1879, of the association of filarian disease with the mosquito. Many observations had already been made, and were made subsequently, on the importance of insects as intermediary hosts in the animal parasites, but the first really great scientific demonstration of a widespread infection through insects was by Theobald Smith, now of Harvard University, in 1889, in a study of Texas fever of cattle.(4) I well remember the deep impression made upon me by his original communication, which in completeness, in accuracy of detail, in Harveian precision and in practical results remains one of the most brilliant pieces of experimental work ever undertaken. It is difficult to draw comparisons in pathology; but I think, if a census were taken among the world's workers on disease, the judgment to be based on the damage to health and direct mortality, the votes would be given to malaria as the greatest single destroyer of the human race. Cholera kills its thousands, plague, in its bad years, its hundreds of thousands, yellow fever, hookworm disease, pneumonia, tuberculosis, are all terribly destructive, some only in the tropics, others in more temperate regions: but malaria is today, as it ever was, a disease to which the word pandemic is specially applicable. In this country and in Europe, its ravages have lessened enormously during the past century, but in the tropics it is everywhere and always present, the greatest single foe of the white man, and at times and places it assumes the proportions of a terrible epidemic. In one district of India alone, during the last four months of 1908, one quarter of the total population suffered from the disease and there were 400,000 deaths—practically all from malaria. Today, the control of this terrible scourge is in our hands, and, as I shall tell you in a few minutes, largely because of this control, the Panama Canal is being built. No disease illustrates better the progressive evolution of scientific medicine. It is one of the oldest of known diseases. The Greeks and Graeco-Romans knew it well. It seems highly probable, as brought out by the studies of W.H.S. Jones of Cambridge, that, in part at least, the physical degeneration in Greece and Rome may have been due to the great increase of this disease. Its clinical manifestations were well known and admirably described by the older writers. In the seventeenth century, as I have already told you, the remarkable discovery was made that the bark of the cinchona tree was a specific. Between the date of the Countess's recovery in Lima and the year 1880 a colossal literature on the disease had accumulated. Literally thousands of workers had studied the various aspects of its many problems; the literature of this country, particularly of the Southern States, in the first half of the last century may be said to be predominantly malarial. Ordinary observation carried on for long centuries had done as much as was possible. In 1880, a young French army surgeon, Laveran by name, working in Algiers, found in the microscopic examination of the blood that there were little bodies in the red blood corpuscles, amoeboid in character, which he believed to be the germs of the disease. Very little attention at first was paid to his work, and it is not surprising. It was the old story of "Wolf, wolf"; there had been so many supposed "germs" that the profession had become suspicious. Several years elapsed before Surgeon-General Sternberg called the attention of the English-speaking world to Laveran's work: it was taken up actively in Italy, and in America by Councilman, Abbott and by others among us in Baltimore. The result of these widespread observations was the confirmation in every respect of Laveran's discovery of the association with malaria of a protozoan parasite. This was step number three. Clinical observation, empirical discovery of the cure, determination of the presence of a parasite. Two other steps followed rapidly. Another army surgeon, Ronald Ross, working in India, influenced by the work of Manson, proved that the disease was transmitted by certain varieties of mosquitoes. Experiments came in to support the studies in etiology; two of those may be quoted. Mosquitoes which had bitten malarial patients in Italy were sent to London and there allowed to bite Mr. Manson, son of Dr. Manson. This gentleman had not lived out of England, where there is now no acute malaria. He had been a perfectly healthy, strong man. In a few days following the bites of the infected mosquitoes, he had a typical attack of malarial fever.

The other experiment, though of a different character, is quite as convincing. In certain regions about Rome, in the Campania, malaria is so prevalent that, in the autumn, almost everyone in the district is attacked, particularly if he is a newcomer. Dr. Sambon and a friend lived in this district from June 1 to September 1, 1900. The test was whether they could live in this exceedingly dangerous climate for the three months without catching malaria, if they used stringent precautions against the bites of mosquitoes. For this purpose the hut in which they lived was thoroughly wired, and they slept under netting. Both of these gentlemen, at the end of the period, had escaped the disease.

Then came the fifth and final triumph—the prevention of the disease. The anti-malarial crusade which has been preached by Sir Ronald Ross and has been carried out successfully on a wholesale scale in Italy and in parts of India and Africa, has reduced enormously the incidence of the disease. Professor Celli of Rome, in his lecture room, has an interesting chart which shows the reduction in the mortality from malaria in Italy since the preventive measures have been adopted—the deaths have fallen from above 28,000 in 1888 to below 2000 in 1910. There is needed a stirring campaign against the disease throughout the Southern States of this country.

The story of yellow fever illustrates one of the greatest practical triumphs of scientific medicine; indeed, in view of its far-reaching commercial consequences, it may range as one of the first achievements of the race. Ever since the discovery of America, the disease has been one of its great scourges, permanently endemic in the Spanish Main, often extending to the Southern States, occasionally into the North, and not infrequently it has crossed the Atlantic. The records of the British Army in the West Indies show an appalling death rate, chiefly from this disease. At Jamaica, for the twenty years ending in 1836, the average mortality was 101 per thousand, and in certain instances as high as 178. One of the most dreaded of all infections, the periods of epidemics in the Southern States have been the occasions of a widespread panic with complete paralysis of commerce. How appalling the mortality is may be judged from the outbreak in Philadelphia in 1793, when ten thousand people died in three months.(5) The epidemics in Spain in the early part of the nineteenth century were of great severity. A glance through La Roche's great book(6) on the subject soon gives one an idea of the enormous importance of the disease in the history of the Southern States. Havana, ever since its foundation, had been a hotbed of yellow fever. The best minds of the profession had been attracted to a solution of the problem, but all in vain. Commission after commission had been appointed, with negative results; various organisms had been described as the cause, and there were sad illustrations of the tragedy associated with investigations undertaken without proper training or proper technique. By the year 1900, not only had the ground been cleared, but the work on insect-borne disease by Manson and by Ross had given observers an important clue. It had repeatedly been suggested that some relation existed between the bites of mosquitoes and the tropical fevers, particularly by that remarkable student, Nott of Mobile, and the French physician, Beauperthuy. But the first to announce clearly the mosquito theory of the disease was Carlos Finlay of Havana. Early in the spring of 1900, during the occupation of Cuba by the United States, a commission appointed by Surgeon-General Sternberg (himself one of the most energetic students of the disease) undertook fresh investigations. Dr. Walter Reed, Professor of Bacteriology in the Army Medical School, was placed in charge: Dr. Carroll of the United States Army, Dr. Agramonte of Havana and Dr. Jesse W. Lazear were the other members. At the Johns Hopkins Hospital, we were deeply interested in the work, as Dr. Walter Reed was a favorite pupil of Professor Welch, a warm friend of all of us, and a frequent visitor to our laboratories. Dr. Jesse Lazear, who had been my house physician, had worked with Dr. Thayer and myself at malaria, and gave up the charge of my clinical laboratory to join the commission.

Many scientific discoveries have afforded brilliant illustrations of method in research, but in the work of these men one is at a loss to know which to admire more—the remarkable accuracy and precision of the experiments, or the heroism of the men—officers and rank and file of the United States Army; they knew all the time that they were playing with death, and some of them had to pay the penalty! The demonstration was successful—beyond peradventure—that yellow fever could be transmitted by mosquitoes, and equally the negative proposition—that it could not be transmitted by fomites. An interval of twelve or more days was found to be necessary after the mosquito has bitten a yellow fever patient before it is capable of transmitting the infection. Lazear permitted himself to be bitten by a stray mosquito while conducting his experiments in the yellow fever hospital. Bitten on the thirteenth, he sickened on the eighteenth and died on the twenty-fifth of September, but not until he had succeeded in showing in two instances that mosquitoes could convey the infection. He added another to the long list of members of the profession who have laid down their lives in search of the causes of disease. Of such men as Lazear and of Myers of the Liverpool Yellow-Fever Commission, Dutton and young Manson, may fitly be sung from the noblest of American poems the tribute which Lowell paid to Harvard's sons who fell in the War of Secession:

Fortunately, the commander-in-chief at the time in Cuba was General Leonard Wood, who had been an army surgeon, and he was the first to appreciate the importance of the discovery. The sanitation of Havana was placed in the hands of Dr. Gorgas, and within nine months the city was cleared of yellow fever, and, with the exception of a slight outbreak after the withdrawal of the American troops, has since remained free from a disease which had been its scourge for centuries. As General Wood remarked, "Reed's discovery has resulted in the saving of more lives annually than were lost in the Cuban War, and saves the commercial interest of the world a greater financial loss each year than the cost of the Cuban War. He came to Cuba at a time when one third of the officers of my staff died of yellow fever, and we were discouraged at the failure of our efforts to control it." Following the example of Havana other centres were attacked, at Vera Cruz and in Brazil, with the same success, and it is safe to say that now, thanks to the researches of Reed and his colleagues, with proper measures, no country need fear a paralyzing outbreak of this once dreaded disease.

The scientific researches in the last two decades of the nineteenth century made possible the completion of the Panama Canal. The narrow isthmus separating the two great oceans and joining the two great continents, has borne for four centuries an evil repute as the White Man's Grave. Silent upon a peak of Darien, stout Cortez with eagle eye had gazed on the Pacific. As early as 1520, Saavedra proposed to cut a canal through the Isthmus. There the first city was founded by the conquerors of the new world, which still bears the name of Panama. Spaniards, English and French fought along its coasts; to it the founder of the Bank of England took his ill-fated colony; Raleigh, Drake, Morgan the buccaneer, and scores of adventurers seeking gold, found in fever an enemy stronger than the Spaniard. For years the plague-stricken Isthmus was abandoned to the negroes and the half-breeds, until in 1849, stimulated by the gold fever of California, a railway was begun by the American engineers, Totten and Trautwine, and completed in 1855, a railway every tie of which cost the life of a man. The dream of navigators and practical engineers was taken in hand by Ferdinand de Lesseps in January, 1881. The story of the French Canal Company is a tragedy unparalleled in the history of finance, and, one may add, in the ravages of tropical disease. Yellow fever, malaria, dysentery, typhus, carried off in nine years nearly twenty thousand employees. The mortality frequently rose above 100, sometimes to 130, 140 and in September, 1885, it reached the appalling figure of 176.97 per thousand work people. This was about the maximum death rate of the British Army in the West Indies in the nineteenth century.

When, in 1904, the United States undertook to complete the Canal, everyone felt that the success or failure was largely a matter of sanitary control. The necessary knowledge existed, but under the circumstances could it be made effective? Many were doubtful. Fortunately, there was at the time in the United States Army a man who had already served an apprenticeship in Cuba, and to whom more than to anyone else was due the disappearance of yellow fever from that island. To a man, the profession in the United States felt that could Dr. Gorgas be given full control of the sanitary affairs of the Panama Zone, the health problem, which meant the Canal problem, could be solved. There was at first a serious difficulty relating to the necessary administrative control by a sanitary officer. In an interview which Dr. Welch and I had with President Roosevelt, he keenly felt this difficulty and promised to do his best to have it rectified. It is an open secret that at first, as was perhaps only natural, matters did not go very smoothly, and it took a year or more to get properly organized. Yellow fever recurred on the Isthmus in 1904 and in the early part of 1905. It was really a colossal task in itself to undertake the cleaning of the city of Panama, which had been for centuries a pest-house, the mortality in which, even after the American occupation, reached during one month the rate of 71 per thousand living. There have been a great many brilliant illustrations of the practical application of science in preserving the health of a community and in saving life, but it is safe to say that, considering the circumstances, the past history, and the extraordinary difficulties to be overcome, the work accomplished by the Isthmian Canal Commission is unique. The year 1905 was devoted to organization; yellow fever was got rid of, and at the end of the year the total mortality among the whites had fallen to 8 per thousand, but among the blacks it was still high, 44. For three years, with a progressively increasing staff which had risen to above 40,000, of whom more than 12,000 were white, the death rate progressively fell.

Of the six important tropical diseases, plague, which reached the Isthmus one year, was quickly held in check. Yellow fever, the most dreaded of them all, never recurred. Beri-beri, which in 1906 caused sixty-eight deaths, has gradually disappeared. The hookworm disease, ankylostomiasis, has steadily decreased. From the very outset, malaria has been taken as the measure of sanitary efficiency. Throughout the French occupation it was the chief enemy to be considered, not only because of its fatality, but on account of the prolonged incapacity following infection. In 1906, out of every 1000 employees there were admitted to the hospital from malaria 821; in 1907, 424; in 1908, 282; in 1912, 110; in 1915, 51; in 1917, 14. The fatalities from the disease have fallen from 233 in 1906 to 154 in 1907, to 73 in 1908 and to 7 in 1914. The death rate for malarial fever per 1000 population sank from 8.49 in 1906 to 0.11 in 1918. Dysentery, next to malaria the most serious of the tropical diseases in the Zone, caused 69 deaths in 1906; 48 in 1907; in 1908, with nearly 44,000, only 16 deaths, and in 1914, 4.(*) But it is when the general figures are taken that we see the extraordinary reduction that has taken place. Out of every 1000 engaged in 1908 only a third of the number died that died in 1906, and half the number that died in 1907.

In 1914, the death rate from disease among white males had fallen to 3.13 per thousand. The rate among the 2674 American women and children connected with the Commission was only 9.72 per thousand. But by far the most gratifying reduction is among the blacks, among whom the rate from disease had fallen to the surprisingly low figure in 1912 of 8.77 per thousand; in 1906 it was 47 per thousand. A remarkable result is that in 1908 the combined tropical diseases—malaria, dysentery and beri-beri—killed fewer than the two great killing diseases of the temperate zone, pneumonia and tuberculosis—127 in one group and 137 in the other. The whole story is expressed in two words, EFFECTIVE ORGANIZATION, and the special value of this experiment in sanitation is that it has been made, and made successfully, in one of the great plague spots of the world.

Month by month a little, gray-covered pamphlet was published by Colonel Gorgas, a "Report of the Department of Sanitation of the Isthmian Canal Commission." I have been one of the favored to whom it has been sent year by year, and, keenly interested as I have always been in infectious diseases, and particularly in malaria and dysentery, I doubt if anyone has read it more faithfully. In evidence of the extraordinary advance made in sanitation by Gorgas, I give a random example from one of his monthly reports (1912): In a population of more than 52,000, the death rate from disease had fallen to 7.31 per thousand; among the whites it was 2.80 and among the colored people 8.77. Not only is the profession indebted to Colonel Gorgas and his staff for this remarkable demonstration, but they have offered an example of thoroughness and efficiency which has won the admiration of the whole world. As J. B. Bishop, secretary of the Isthmian Canal Commission, has recently said: "The Americans arrived on the Isthmus in the full light of these two invaluable discoveries (the insect transmission of yellow fever and malaria). Scarcely had they begun active work when an outbreak of yellow fever occurred which caused such a panic throughout their force that nothing except the lack of steamship accommodation prevented the flight of the entire body from the Isthmus. Prompt, intelligent and vigorous application of the remedies shown to be effective by the mosquito discoveries not only checked the progress of the pest, but banished it forever from the Isthmus. In this way, and in this alone, was the building of the canal made possible. The supreme credit for its construction therefore belongs to the brave men, surgeons of the United States Army, who by their high devotion to duty and to humanity risked their lives in Havana in 1900-1901 to demonstrate the truth of the mosquito theory."(7)

One disease has still a special claim upon the public in this country. Some fourteen or fifteen years ago, in an address on the problem of typhoid fever in the United States, I contended that the question was no longer in the hands of the profession. In season and out of season we had preached salvation from it in volumes which fill state reports, public health journals and the medical periodicals. Though much has been done, typhoid fever remains a question of grave national concern. You lost in this state(7a) in 1911 from typhoid fever 154 lives, every one sacrificed needlessly, every one a victim of neglect and incapacity. Between 1200 and 1500 persons had a slow, lingering illness. A nation of contradictions and paradoxes—a clean people, by whom personal hygiene is carefully cultivated, but it has displayed in matters of public sanitation a carelessness simply criminal: a sensible people, among whom education is more widely diffused than in any other country, supinely acquiesces in conditions often shameful beyond expression. The solution of the problem is not very difficult. What has been done elsewhere can be done here. It is not so much in the cities, though here too the death rate is still high, but in the smaller towns and rural districts, in many of which the sanitary conditions are still those of the Middle Ages. How Galen would have turned up his nose with contempt at the water supply of the capital of the Dominion of Canada, scourged so disgracefully by typhoid fever of late! There is no question that the public is awakening, but many State Boards of Health need more efficient organization, and larger appropriations. Others are models, and it is not for lack of example that many lag behind. The health officers should have special training in sanitary science and special courses leading to diplomas in public health should be given in the medical schools. Were the health of the people made a question of public and not of party policy, only a skilled expert could possibly be appointed as a public health officer, not, as is now so often the case, the man with the political pull.

It is a long and tragic story in the annals of this country. That distinguished man, the first professor of physic in this University in the early years of last century, Dr. Nathan Smith, in that notable monograph on "Typhus Fever" (1824), tells how the disease had followed him in his various migrations, from 1787, when he began to practice, all through his career, and could he return this year, in some hundred and forty or one hundred and fifty families of the state he would find the same miserable tragedy which he had witnessed so often in the same heedless sacrifice of the young on the altar of ignorance and incapacity.