Simon Flexner, infectious diseases pioneer

Photo of Simon Flexner
Simon Flexner. circa 1930s. Courtesy of the Rockefeller Archive Center. Source,

Infectious diseases shaped the life of Simon Flexner, who rose from humble beginnings to become one of the most successful and prominent scientists in American medicine. His contributions to the field of infectious diseases were legion. He became the first chairman of pathology at the prestigious University of Pennsylvania and the first director of the newly created Rockefeller Institute.

He traced his origins to a small town in Bohemia near the Bavarian border. There the family had fallen on hard times and decided to send the thirteen-year-old boy Moritz, later to become Simon’s father, to be raised by an uncle in Strasbourg. But by 1850 Moritz had developed unpopular and dangerous political associations and decided to move on. Leaving without a penny in his pocket and no connections in America, he traveled steerage to New York, then set out with five companions to New Orleans. But an epidemic of yellow fever struck the city and all his companions died. Moritz survived thanks to the good care of the Catholic nuns at the Charité Hospital. When he recovered he left what he regarded an accursed city, and went up the river to Louisville. He worked as a peddler selling dry goods. In 1856 he married and had nine children.1

Simon was number four. He was mischievous and inattentive in school, often playing pranks on other boys or in trouble, and got himself fired from several jobs. He nearly died from typhoid fever, but his mother nursed him, slept in the same bed with him, talked to him, and listened to him. She built up his confidence, and when he recovered he felt “born again.”1  He first worked in his family’s graphic studio but later became an indentured assistant to a local pharmacist.

Work was hard, and he often had to be on call twenty-four hours a day. As part of his job, he had to complete a three-month course in pharmacy each year. This stimulated his interest in science and especially in using a microscope. He avidly read books on anatomy, histology, and bacteriology, and became proficient at examining dermatologic specimens. Then he acquired some local renown by recognizing on a slide that a judge’s tumor had extended beyond the edges of the excised specimen. The judge took him to New York, where Simon helped him to undergo appropriate therapy.

Later Simon achieved a measure of national recognition by publishing in Science a paper on the chemical nature of a granular material he had found in a beehive. Deciding to become a pathologist, he enrolled in a local medical school. He graduated in two years, never having, as he later put it, examined a patient or listened to a heart sound. He then applied for a pathology fellowship at Johns Hopkins University but was rejected. His younger brother Abraham, who by now had become a successful teacher, saved the day by offering to pay his tuition for one year.1

At Hopkins, this unknown young man from Louisville soon impressed his chief, the famous William Henry Welch, by his diligence and intelligence. He began by discovering a tumor of the retina made of rods and cones and gave it an impressive Latin name. He made important observations about the diphtheria bacillus, which led to another publication. His reputation in infectious diseases rising, he was sent to investigate an outbreak of disease among miners, and soon found out they had meningitis. Welch appointed him as his assistant, and in 1893 sent him to further his education on a tour of England, Holland, Germany, and Austria. He met von Recklinghausen, Virchow, and other luminaries, and was impressed by the discipline and efficiency of the German academic institutions. Appointed to the Hopkins faculty, he was elected in 1895, at age thirty-two, to the American College of Physicians. Promotions followed, first to associate and soon to full professor, with commensurate increments in salary. At one time Cornell University offered to pay him a salary of $8,500 per year, an impressive sum for that time, but at the time he decided to remain in Baltimore.

In 1899, however, he received an irresistible offer to become chairman of the department of pathology at the renowned University of Pennsylvania. This was an opportunity too good to pass over. The salary was lower but prestige was great. There was some opposition in Philadelphia from the anti-Semitic factions of the faculty and trustees, but his appointment went through. Before starting work he visited Japan, then went to Manila, a war zone where American troops were dying from typhoid fever, malaria, dengue fever, tuberculosis, and tropical fevers. They also were afflicted by a particularly devastating form of dysentery. Flexner identified the pathogen causing it as a bacillus—it became known as Shigella flexeri.

At the University of Pennsylvania, Flexner developed an excellent staff and worked on experimental dysentery, pancreatitis, hemolysis, and agglutination. From his department emanated papers on tuberculosis of the aorta, esophagus, and intestine as well as on carcinoma of the pancreas, lymphosarcomas, and amoebic abscesses involving the liver and causing perforation of the inferior vena cava. Other papers addressed fatty degeneration of the heart muscle, plague bacillus, anthrax, typhoid infection with intestinal lesions, snake venom, various pathologies associated with kidney disease, tropical dysentery, meningitis, and familial periodic paralysis. He came in great demand as a specialist in infectious diseases, and in 1901 was called to San Francisco where he identified an outbreak of infectious disease as being caused by bubonic plague.

A momentous development occurred in 1901 when John D. Rockefeller decided to found an institute to emulate the Pasteur Institute in Paris. He convened a group led by Flexner’s former chief William Welch. Flexner was invited to join the board and in March 1902 became director of the new institute. In 1903 he married Helen Thomas, a member of a prominent Quaker family in Baltimore. He recruited an array of talented investigators, including Hideyo Noguchi, who later isolated the spirochete causing syphilis. A large institute was built in New York and for the ensuing years made significant contributions to medicine, including an antiserum to meningococcus that reduced mortality from 75% to 25%. In 1908 he was elected to the National Academy of Sciences. Later, his work on poliomyelitis revealed that this was a viral disease and laid the ground for the much later development of a vaccine against the disease. In Puerto Rico, he carried out important work on hookworm infections and tropical sprue. He remained the director of the Institute until 1935.

He received many honors. In 1937 he left the United States to take up a visiting position as Eastman Professor at Oxford University. He died in 1946. His younger brother, Abraham, who had financed his earlier scholarship at Hopkins, carried out a comprehensive study of medical education and in 1912 published the Flexner report, that forever changed medical practice in America.


Further reading

Bendiner E: Simon Flexner: His ‘Rock’ Was for the Ages, Hospital Practice. 1988



GEORGE DUNEA, MD, Editor-in-Chief



Fall 2020  |  Sections  |  Infectious Diseases