The first failed (Japanese) 'isolation' attempt (1924). Note: no definite chemical formula was discovered and a dying rat was the only forced witness.
Source:
1/5 science.org/doi/10.1126/sc…
The 2nd failed 'isolation' attempt (1937) where the chemical formula was given (by Karrer) even before the isolation experiment. Since Vitamin A was unknown, how could one be sure 60 rats were "depleted of Vitamin A"? #ReificationFallacy