The Evolution of Modern Medicine / A Series of Lectures Delivered at Yale University on the Silliman Foundation in April, 1913

by Sir William Osler

SANITATION

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.

(3) Journal Linnaean Society, London, 1879, XIV, 304-311.
(4) Medical News, Philadelphia, 1889, LV, 689-693, and monograph
with Kilborne, Washington, 1893.

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.

(5) Matthew Carey: A Short Account of the Malignant Fever,
Philadelphia, 1793.
(6) R. La Roche: Yellow Fever, 2 vols., Philadelphia, 1855.

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:

Many in sad faith sought for her,
Many with crossed hands sighed for her;
But these, our brothers, fought for her,
At life's dear peril wrought for her,
So loved her that they died for her.