Letter from A. D. Hershey to Michael Heidelberger

In this letter Hershey replied to Heidelberger's critical comments regarding Hershey's efforts to use bacteriophages, viruses that infect bacteria, to study the kinetics--the rate and mechanisms--of immune reactions. Hershey also discussed emerging conceptions of antibody heterogeneity, the idea that the multiple chemical bonds established by multivalent antibodies with two or more antigens are formed at different rates.