In November 1973 Newcastle disease suddenly appeared in Northern Ireland, where the viscerotropic disease had not been seen in 3½ years and the two Irelands had been regarded as largely disease free for 30 years. It was successfully controlled with only 36 confirmed affected layer flocks, plus 10 more slaughtered as ‘dangerous contacts’. Contemporary investigations failed to reveal the source of the Irish epidemic. Using archival virus samples from most of the affected flocks, RT–PCR was conducted with primers selected for all six NDV genes. Phylogenetic analyses of three genes, HN, M and F, confirmed vaccine as the cause of one of the outbreaks. The other six samples were identical and closely related to previous outbreaks in the United States and western Europe initiated by infected imported Latin American parrots. The probable cause of the epidemic followed from the importation from The Netherlands of bulk feed grains contaminated with infected pigeon faeces.

In the Renaissance, religious and political confrontations generated an intensified awareness of the self which marks a decisive phase in the evolution of human personality, whose study may be entitled Historical Psychology. Alienation from religious and political strife turned the interests of Petrarch and Montaigne toward their own minds, Marot's persecution for heresy developed his self-awareness in L'Enfer, followed by Ronsard's self-defensive autobiography in his Reply to Insults. Such models prefigure Milton's authorial intrusions of Paradise Lost. Shakespeare illustrates the creative impact of religious controversy by enriching the hints of Lollardry in Falstaff with a wide variety of Puritan affectations in the Elizabethan period. The Protestant attacks on Machiavelli also help in developing the character of Richard III and similar introverted creations, as T. S. Eliot notes. By the time of Marvell, personality is considered essentially artificial and willed—an inheritance from which Swift, the Romantics, and many modern authors have profited. Historical Psychology is thus a necessary tool if we are to handle the development of literary tradition.