Today's Duality
Post-1910 to present — both threads running in parallel, one licensed, one at the margins.
Germ Theory
Alexander Fleming discovers penicillin; by the 1940s, mass-produced antibiotics become germ theory's signature clinical success story.
The CDC is founded, institutionalizing germ-theory-based public health surveillance in the U.S.
Jonas Salk's polio vaccine is released — another major public triumph credited to the theory.
The WHO declares smallpox eradicated worldwide — still germ theory's most frequently cited win.
The biomedical model remains the licensed standard of care across nearly all of Western medicine, insurance, and regulation.
Terrain Theory
Royal Rife's frequency-based research proposes that microorganisms change form under different conditions, echoing Béchamp's pleomorphism; his claims remain controversial and were never accepted by mainstream science.
Gaston Naessens, continuing microzymian-style (“somatid”) research, is tried in Quebec over his unlicensed cancer treatment 714X — and is acquitted by a jury in under an hour.
The Institute for Functional Medicine is founded, reintroducing terrain-adjacent, root-cause approaches into a licensed clinical setting for the first time since Flexner.
The Human Microbiome Project maps the microbial ecosystem living in and on the human body, establishing that it measurably shapes immune function and disease susceptibility — research mainstream science doesn't label “terrain theory,” but which terrain advocates point to as resonant with its core claim.
Terrain-adjacent approaches persist outside, and increasingly at the edges of, licensed medicine: functional and integrative medicine, microbiome research, and nutrition-based prevention.
A century after Flexner, both threads Pasteur and Béchamp began are still running — one holding the license, the other holding the argument that health starts inside the body, not outside it.