From demonic possession to contagious afflictions

In 1751 Nils Gissler (1715–1771), disciple of Linnaeus and the first practicing physician in northern Sweden, suffered a bout of mental illness lasting several months. Unusually, his account features the devil – not in visions but as a decidedly physical force penetrating his body and senses. Overcoming these attacks required mental strength and faith in God’s grace, an experience Gissler described many years later in a detailed account that included comparable cases from his own medical practice. In his final years, he seemingly theorised afflictions as contagious. This chapter will first examine how Gissler implemented his experiences in his medical practice; second, locate his medico-theological praxis within Enlightenment ideas and the medicalisation of society; and third, analyse the conception of contagion as a possible turning point in his medical thought.