Letter from Richard Willstatter to Michael Heidelberger

In this letter Heidelberger's former mentor, the organic chemist and Nobel Laureate Richard Willstatter, acknowledged initial doubts regarding Heidelberger's and Oswald Avery's findings in 1923 and 1924 that powerful antigens of type-specific pneumococcus bacteria are polysaccharides. Willstatter had instead thought that "adsorbed traces of a highly reactive unknown substance" might determine the bacteria's pathogenicity. Since then, however, he admitted that it had become clearer that Heidelberger's work "created a great new advance in the field and that you have prevailed completely."