Actinomycosis is a rare local specific infectious disease, due to the actinomyces, or ray fungus. The actinomyces is a streptothrix, and grows in colonies which are just visible to the naked eye, and these colonies, on microscopical examination, are found to consist of three elements–filaments, cocci, and clubs. In young cultures they stain uniformly, and are Gram-positive. The streptothrix gives rise to a hard, slow-growing tumour, going on to ulceration, with a thin sero-purulent discharge, containing yellow granules in which the ray fungus can be found. The organism is found growing on cereals, especially barley, and commonly infects cattle. Man is infected in the same way, and the disease is generally met with in farmers, corn-eaters, graziers, etc., especially if the patient has the habit of chewing straw, the infection most commonly occurring in the tongue, jaw, and spreading thence to the skin of the face and neck.