Two years after his death, William Mayo said of Plummer's work on the thyroid, “Developing many new things along many diverse lines, always he came back to his fundamental work on the thyroid gland, in which he was no less than a genius.”
Plummer was often characterized as a genius by the Mayo brothers and his colleagues for his groundbreaking ideas, but also because of his peculiar, distracted behavior, Fye said.
Dr. William Braasch, a Mayo Clinic colleague, wrote of Plummer in his book, Early Days in the Mayo Clinic, “He had a complex personality. The casual observer would gain the impression that he was an eccentric, absent-minded person. However, his apparent diffidence was usually explained by complete absorption in solving some problem of the moment, so that when spoken to he often made no reply.”
Fye said that although such eccentric qualities are not usually appealing for a physician, his innovative mind likely made up for his flaws. “If you're trying to build a practice, that wouldn't be the kind of person you'd hire,” he said. “But clearly, his other attributes sort of trumped whatever shortcomings there were.”