To the editor:

Peter Medawar once pointed out that when a scientist describes his work for publication, historical revisionism inevitably intrudes1. No mention is made of false starts, wrong interpretations or rejected data; the results are presented in a logical order, as though the initial questions were obvious and led in a straight line to the results. How then is the historian to make sense of the process and to help us to understand the cultural richness and scientific complexity of our past and how we got where we are today? Only by digging deeper into the scientist's notebooks, correspondence and other private papers. This can only be done if these materials are deposited in an accessible archive.

Paul Ehrlich, who shared the 1908 Nobel Prize for his immunological research, was the leading medical scientist of the late nineteenth and early twentieth centuries. No scientist opened more fields of biomedicine than Ehrlich, a founder of histology, hemato-logy and chemotherapy in addition to immunology. Now, 90 years after Ehrlich's death, the Rockefeller Archive Center has obtained a newly discovered treasure trove of his manuscripts.

The acquisition is remarkable because during the Nazi regime this Jewish scientist became a 'non-person' and many of his papers were scattered. After the Second World War, Ehrlich's grandson searched throughout Europe for Ehrlich's papers and eventually deposited the entire collection at the Rockefeller Archive Center, establishing the most comprehensive collection of Ehrlich's papers in the world.

Among the newly acquired materials are about 20 laboratory notebooks, some dating from Ehrlich's 1880s studies using aniline dyes to identify previously unknown types of blood cells and others appearing to be from his 1905–1910 systematic screening of hundreds of chemical compounds to discover a 'magic bullet' drug to treat syphilis. In addition, there are more than 1,000 so-called 'blöcke' — essentially oversized index cards with Ehrlich's handwritten notes on them. These include notes to himself, lists of things to do and things to buy, and suggestions to his colleagues about how to do experiments. The new material fills gaps in the original collection and will add to the historical understanding of how this great scientist worked.

The field of immunology is fortunate to have available this treasure of Ehrlich material, which the Rockefeller Archive Center makes available to researchers by appointment. Moreover, the center also offers special grants to support research in the Paul Ehrlich Collection2.

The present value of these 100-year-old Ehrlich papers points up the importance of keeping research notebooks and other pertinent papers for the use of future historians. Most universities and research institutes have established formal archives, and those immunologists (and other scientists) who have made significant contributions should be encouraged to arrange to have their papers safeguarded in this way.