The second is called the endogenous theory, which suggests that A. bovis is naturally found in the mouths of healthy animals.[10] This theory has been supported by several researchers over the years as they have been able to isolate multiple strains of Actinomyces. In 1905, Wright described isolation techniques and colony morphology in different media.[11] A. bovis has been isolated from tonsillar crypts, infected teeth, and dental scum of normal mouths from human and animal patients.[12][13] Several researchers were then able to conclude that the bacteria are part of the normal flora of the mouth, making the mouth a source of disease.