1. The absorption of typhus sera (human or antityphus horse serum) with Proteus X-19 removes only the Proteus agglutinins, leaving the Rickettsia agglutinins intact.
2. The absorption of typhus sera with Mexican Rickettsiae removes the agglutinins for both the Rickettsia and Proteus X-19.
3. While normal or formalinized Rickettsiae are not agglutinated by anti-Proteus serum, these organisms—when formalinized and heated at 75°C.—become agglutinable by such serum.
4. The absorption of anti-Proteus serum with Mexican Rickettsiae removes agglutinins for formalinized and heated Rickettsiae but does not affect those for Proteus X-19.