The agents of actinomycosis are now known to be endogenous organisms of the mucous membranes, in most cases Actinomyces israelii, a species named after surgeon James Israel, who first discovered its presence in humans in the late 1870s.
In 1877, pathologist Otto Bollinger described the presence of Actinomyces bovis in cattle, and shortly afterwards, James Israel discovered Actinomyces israelii in humans.