Dates: b. 1863; 1900 to Penn; 1903 to Rockefeller; d. 1946
Locations: First Assistant and Assist. Prof. of Path. Anatomy, (1894‑1898); Prof. Pathological Anatomy, Hopkins (1898‑1899); Professor of Pathology, in both Medical and Veterinary Depts. University of Pennsylvania; Pennsylvania Hospital (1899‑1904); Director, Rockefeller Institute for Medical Research (1901‑1935)
Training: MD Univ. Louisville 1889; under Welch at Hopkins; in Strasbourg under Recklinghausen; sent to Philippines and India to study Plague;
Fields: medical; immunology; BACT‑NOM
Publications: "Mode of Infection, Means of Prevention, and Specific Treatment of Epidemic Meningitis," Rockefeller Inst. for Med. Res. (1917): 45; with P.F. Clark and Paul A. Lewis, Poliomyelitis Papers (New York: Rockefeller Inst., 1909)
SAB Involvement: Charter SAB member; SAB council member 1901, 1906; Added to SAB Comm. on Methods of Identification of Species 1910‑; possible session chair of human pathology 1916 meeting; resigned without paying dues 1916; Pres. AAPB 1905
Archive Files: See obit, by Eugene L. Opie, "Simon Flexner, M.D. 1863‑1946 (Obituary)," Arch. Path. 42 (1946): 234‑242; Stanhope Bayne‑Jones, "Simon Flexner (1863‑1946)," Yearbook of the American Philosophical Society (1946): 289‑297; “Simon Flexner and Medical Discovery” Science 107, June 11, 1948; “Recollections of a Street Corner Pump and the Progress of Sixty Years” (80th birthday testimonial) Science 98:2532, 1943; Encyc. American Biog. (1974); Nat. Cyc. American Biog. 52, 1970; ANB; DSB; DAB
Flexner was a fellow of pathology under Welch for eight years at Hopkins, filling the position of first assistant and then Prof. of Pathology after Councilman left for Harvard. With Gay and others, Flexner was part of a Hopkins expedition to investigate prevalent diseases in the Philippines among U.S. troops.
Succeeded Guiteras as professor of Pathology in both Medical and Veterinary Dept. In 1901, Flexner was part of the Federal Commission to investigate plague in San Francisco’s Chinatown. At Penn, Flexner studied summer diarrhea in infants. While in Manila, he himself had isolated an organism from an American soldier in an epidemic of 1900, and thought that he had confirmed Shiga's findings. However, time showed that the two organisms were dissimilar.
At the 1900 meeting of the SAB, Flexner presented on "The Bacillus dysenteriae," which was discussed by Sedgwick. At the 1906 SAB meeting, he outlined "The Enzymatic Properties of Diplococcus intracellularis," which was discussed by Winslow, Park, Ohlmacher, Kinyoun, and Hiss. Apparently, the organism survived only a short while on culture media, with degeneration and loss of staining power, etc. coming quickly. Flexner did note that the enzyme responsible for this auto degeneration also dissolved B. typhosis, B. coli, B. pyocyaneus, B. anthracis, M. catarrhalis, and to a lesser degree Staph. aureus.
Flexner is best known as the first director of the Rockefeller Institute for Medical Research, and the developer of the anti meningococcal serum. His work on the experimental transmission of poliomyelitis in monkeys was not as successful, as he maintained that the normal route of human infection was nose and throat, not mosquitoes. Additionally, Flexner and Noguchi reported finding globoid bodies in material extracted from monkeys suffering from poliomyelitis and also from human cases. Injections of normal monkeys with such cultures produced the typical experimental disease. However, few researchers could confirm these findings.
The work on anti meningitis serum is instructive in that it shows the paradigmatic model of diphtheria anti toxin. Flexner inoculated horses, building up anti toxin, and separated and concentrated the serum. He tested the product in 1905 among the various types of experimental animals, and in 1908 began studies on humans. At first, the success rate of the serum was in doubt. In 1913, he studied the effectiveness of serum in 1,300 human cases, finding about a 70% recovery rate and fewer sequelae, and an even higher success rate when the serum as administered in the first three days of the disease.
Flexner also conducted extensive studies on experimental sarcomas, and experimental colitis. His pathological studies included research on thrombosis in 1902.