The Prussian state and microbiological research--Friedrich Loeffler and his approach to the "invisible" virus.

When Loeffler took his first steps in the newly-emerging field of virology, the aim and the methods of his research activities were influenced by two different issues: 1) Loeffler was rooted in the scientific paradigm of bacteriology, but during the progress of his research on foot-and-mouth-disease (FMD) he recognized that the classical techniques derived from bacteriology were useless in identifying the agent of this disease. Thus he focussed on the properties of the pathogen and--though he could not find a method in order to visualize the 'virus'--he tried to develop a vaccine against the disease. 2) The Prussian Government was highly interested in effectively combatting FMD. In 1897 Loeffler was appointed by the Ministry of Cultural Affairs to the newly-established commission for exploring that disease. The agricultural lobbies and the public pursued the activities of the commission with a mixture of hope and serious scepticism and demanded convincing results. These circumstances caused a considerable degree of political pressure on Loeffler, pressure which determined that his research activities would take a pragmatic approach, that he would avoid sophisticated reflections and trials on the nature of the 'virus', and that his research strategies would have as a goal the development of an effective immunization.