So now he had two powerful data points. Mice with an immature thymus could get leukemia. Mice with no thymus whatsoever appeared to be defenseless against disease. Dr. Miller hypothesized the heretical—that the thymus was of tremendous significance. He then took one more key step to prove it. It’s a brilliant idea that he nonetheless dismisses as obvious. He took two mice. He removed the thymus from one at birth. Then he took skin from the other mouse and grafted it onto the one without a thymus.
