Guys read this and answer just one question plzzz

i will follow, like, brainliest , etc

in 1987 a strange nerve disease attacked the people in the dutch east indies. the disease was beriberi (pronounced berry-berry). those who fell ill could not eat and became paralyzed and could not move. scientists believed the disease may have been caused by bacteria in the blood.
the scientists used “infected” blood as the variable in their experiment. in the manipulated group they injected chickens with blood from beriberi patients. in the control group they did not inject chickens with blood from beriberi patients. the injected chickens became sick. however, so did the group of chickens that were not injected with the blood from beriberi patients. the scientists were confused by these results.
one of the scientists, dr. christiaan eijkman (pronounced ick–man), noticed something about the experiment. normally all the chickens eat whole-grain rice, but during the experiment, the chickens ate white rice. whole-grain rice or brown rice is covered with a seed coat. the seed coat contains a vitamin called thiamine. all of the chickens in the experiment ate white rice which does not have the seed coat. dr. eijkman researched this interesting case further. he found that white rice lacked thiamine (pronounced thigh–a-mean), a vitamin necessary for good health, which is also linked to beriberi.

question: . if you were dr. eijkman, how could you test your hypothesis?