The disease is very common among cattle in certain regions, and causes the condemnation of many animals in every large stockyard establishment where inspection is careful and scientific. It occurs oftener in young than in old animals, and most frequently in those which come from valley regions and marshes. In animals infection occurs almost invariably through the mouth, which is easily explained by the fact that, in grazing, the lips, tongue, and gums are likely to be irritated and infected at any time from soil containing these fungi along with growing grain. The path of infection is usually by the mouth, while accident seems to determine whether the infection shall manifest itself mainly in the intestinal canal or the respiratory tract. In animals there is less tendency to suppuration than in man, the infection in man being usually a mixed one. The name _lumpy jaw_, so generally given to the affection, is indicative of the most conspicuous lesion in cattle, for the organism, having once invaded the gum, for instance, passes quickly to the bone, or, having involved the tongue, is not slow to infect the lymphatics of that region. In consequence we have tumors, often of inordinate size, which may involve the bones or the soft parts and cause great disfigurement, along with necrosis, leading eventually to the death of the animal. These tumors are essentially _granulation tumors_ due to the presence of a specific irritant--the _actinomycis_--which acts here as do the tubercle bacillus, the lepra bacillus, etc., in other infectious granulomata. In man the disease is generally accompanied by abscess formation, the pus containing the distinctive yellow gritty particles which are found in no other disease. The strong resemblance between the lymphoid cells of this form of granuloma and the embryonal cells of sarcoma has permitted the perpetuation of confusion between these two neoplasms. [Illustration: FIG. 19 Actinomycosis in man. (Lexer.)]