Historical article: Titration studies and the structure of DNA.

During the period of 1946-1956 ideas on the structure of the nucleic acids, especially DNA, were profoundly influenced by physico-chemical studies and, in particular, by electrometric titration studies pioneered by J. Masson Gulland and D.O.

The black death past and present. 2. Some historical problems.

This paper looks, from a historian's point of view, at the black death and the epidemics of plague which succeeded it in Europe from the fourteenth to the seventeenth centuries. It identifies the controversial questions, of medical as well as historical interest, which have been raised by recent work. These include the origins of plague epidemics, the role of rodents and insect vectors in them, and the reasons for their disappearance from western Europe.