Two weeks ago, at the end of an interview about whether polio really can be eradicated, Bill Gates muttered aloud to an aide escorting the interviewer: “I’ve got to get my D. A. Henderson response down better.”

By that he meant that as long as he was committing his fortune and prestige to the battle against polio  as he did that day in an announcement at the former Manhattan home of Franklin D. Roosevelt  he would need a stronger riposte to journalists quoting Dr. Henderson’s powerful arguments that the virus is just too elusive to subdue.

In a world of quotable medical experts, why does it matter what one particular expert thinks? Because, for better or worse, the mantle has been wrapped around the venerable 82-year-old Donald A. Henderson that he is “The Man Who Wiped Out Smallpox.”

(In truth, the smallpox fight  the only successful one so far against a human illness  had many generals. One is Dr. William H. Foege, 74, a former director of the Centers for Disease Control who is now a senior adviser to the Bill and Melinda Gates Foundation and who fervently believes that polio can be eradicated. But over the years, Dr. Henderson has patiently explained his doubts, in persuasive detail, to many medical journalists calling him with questions about any disease eradication effort.)