Infections in the floor of the mouth may extend into the deep facial planes of the neck and produce a cellulitis which has a decided tendency to terminate in gangrene or abscess formation. Ludwig originally described the condition as a gangrenous induration of the neck; Vincent refers to the disease as a foetid para-buccal abscess. The primary focus occurs about the teeth in most instances (Muckleston, Van Wagenen and Costello, Ashhurst). These observers, among others recovered an aerobic streptococcus from the cervical lesion, more rarely staphylococci or other aerobic organisms, which they regarded as presumably the causal agent. However, no reference is made to anaerobic studies. Melchoir found fusiform bacilli and cocci in 4 cases; fusiform bacilli alone in one case; spirochetes, fusiform bacilli and cocci in another case. More recently, Hansen told me he observed a fatal case of Ludwig's angina in which he found fusiform bacilli and spirochetes in large numbers. It has been demonstrated that local lesions about the teeth generally harbor fuso-spirochetal organisms. These organisms produce a foul abscess or gangrene when introduced into the tissues of animals.,, It therefore seemed reasonable to infer that Ludwig's angina might be due to a fuso-spirochetal infection. The scrapings from the teeth of patients with pyorrhea were inoculated into the inner margin of the gum of the lower posterior teeth in 25 guinea pigs. Each of 5 pigs received 0.25 cc. of pyorrhea material. Four animals remained normal, the fifth, after 5 days, developed an enlarged gland deep in the neck immediately below the mandible. The gland gradually enlarged during the following week and the infection spread to the surrounding cellular tissue.