Letter from Michael Heidelberger to Kai O. Pedersen

In this letter Heidelberger followed up on his visit to the laboratory of Arne Tiselius at the University of Uppsala in the summer of 1934, during which he used ultracentrifugation to determine the size of antibodies molecules. Tiselius was the inventor of the ultracentrifuge, and Uppsala was the first university to build one, in a separate building designed to withstand the vibrations caused by the earliest models.