The Fate of Avirulent Hemolytic Streptococci Injected into the Skin of Normal and Sensitized Rabbits

1. A relatively avirulent strain of hemolytic streptococci injected into the skin of normal rabbits seldom diminished and usually increased in number during the first 5 hours after inoculation but after 12 hours save in exceptional instances the organisms diminished rapidly and disappeared. 2. Hemolytic streptococci injected into the skin of normal rabbits passed rapidly from the site of injection to the regional lymph nodes from which they were recovered in considerable number within 15 minutes. Passage of bacteria from the skin of the abdomen to the inguinal lymph node was greatest within 2 hours after injection and gradually decreased so that few organisms were recovered from the lymph nodes after 7 hours. 3. Hemolytic streptococci that reached the inguinal lymph node passed in small numbers to the distal or iliac lymph node, but this passage save in exceptional instances of progressive infection was limited to a period within 1 hour after inoculation. 4. Avirulent hemolytic streptococci injected into the skin of normal animals penetrated into the blood; they were seldom recovered from the circulating blood but were more frequently found in the spleen. 5. When hemolytic streptococci were injected into the skin of sensitized rabbits they multiplied at the site of injection during the first 5 hours after inoculation and at corresponding time intervals a larger number of organisms were recovered from the sensitized than from normal control animals. Streptococci diminished and disappeared earlier from the skin of control than from that of sensitized rabbits. 6. Hemolytic streptococci injected into the skin of the flank of sensitized rabbits reached the inguinal lymph node in much smaller numbers than in normal rabbits, and this passage from the site of injection to the lymph node save in an occasional instance of progressive local infection ceased after the 1st hour. No streptococci passed from the inguinal to the iliac lymph nodes of sensitized animals and none were found in the blood or internal organs. 7. Histological examination showed that the inflammatory reaction following the injection of hemolytic streptococci into rabbits sensitized to this organism began sooner than in the normal animal; edema was more extensive and both polymorphonuclear leucocytes and large mononuclear cells appeared sooner. The lesion of a sensitized animal was more sharply circumscribed and there was necrosis of tissue, seldom seen in the normal animals. 8. In sensitized animals local injury with necrosis favors the multiplication of relatively avirulent streptococci at the site of entry and explains their survival at a time when they have disappeared in the controls. 9. In association with greater local injury and a more intense inflammatory reaction in the sensitized animal as compared with the normal streptococci are fixed at their site of entry; they pass to adjacent lymph nodes in much smaller number and fail to reach the blood and internal organs.