The collected papers of Paul Ehrlich : why was volume 4 never published?

In the 1950s, Sir Henry Hallett Dale undertook to compile and publish all the scientific papers of Nobel laureate Paul Ehrlich. He was assisted in this venture by Dr. Fred Himmelweit and by Ehrlich's former secretary, Martha Marquardt. A four-volume series was announced, but only three volumes saw the light of day, between 1957 and 1960. This report presents the result of a five-year effort to determine the reason for the failure to complete the undertaking, in which all potential sources were pursued and queried. In the end, the mystery remains unsolved.