THE second case occurred in a lady who, in attempting to bite a hard lozenge, put considerable strain on her left lower central incisor which made the tooth slightly tender. The patient was in quite good health at the time, but about twenty-eight hours after the strain she remembers taking one or two spoonfuls of a milk soup which tasted putrid. By the morning of the second day she felt unwell and the pain and tenderness had increased. On examination, a few hours later, I found the tooth slightly loose and the pulp was dead, though up to the time of this strain the tooth had never given trouble nor was there any sign of caries. I should mention that the pulp of the adjoining left lateral incisor died about ten years previously, and the root canal had been treated and filled at the time and had given no trouble since.The central incisor was opened up and the pulp removed but no pus came. After washing out the cavity a loose dressing of tricresol and formalin was inserted, and hot fomentations and counter-irritants were applied to the buccal sulcus. The pain, however, continued and became so acute that, on seeing the patient twenty-four hours later, I decided to extract the tooth. The apex of the tooth showed signs of commencing absorption. This was three days after the injury. For a time the symptoms -improved, though the swelling did not entirely subside, but on the eighth day they had returned with increased severity, and the mischief began to spread with alarming rapidity from the original localized area of the left central incisor to the right side of the mandible as far as the first molar. Pain, tenderness, and swelling extended along the whole of the right side of the mandible. The patient was obviously ill, and had a tenaperature of 1010 F. and a pulse of 98. I consulted Mr. Tubby, who agreed that the case was one of acute infective periostitis, and we decided to sacrifice the right lower first molar whose pulp had been devitalized some five or six years before, and the left lower lateral incisor just referred to, the pulp of which had died previously. These teeth were extracted under an anaesthetic, and a deep incision was made in the sulcus between the symphysis and the right molar. This time, nearly 3 dr. of pus welled up, and a bacteriological examination revealed large numbers of a tiny streptococcus which at present has not been identified. No other ju-13a 143