The first experiment consisted in radiating minnows with a very low dose of radioactivity, then put them in a tub with non-radiated fish and verify if with time the radiated fish would have transmitted their radioactivity to the non radiated fish: very quickly all the non radiated fish were contaminated!
A similar experiment was performer on mice: using low doses of natural radioactivity, a few mice were radiated, when mixed with non radiated mice in a cage they then contaminated all the other mice previously non radiated.
This second experiment was even more extraordinary because the transmission didn’t take place in water, but the proximity of the other animals was enough to spread the radiation! This could be a long-term effect of medical operators that treat their patients on a bed located on top of natural radiation, even at low doses.