Reactions to antipneumococcal rabbit serum: V. Efffects on reversed passive anaphylaxis of lengthening the interval between constant sensitizing doses of pneumococcal polysaccharide and constant shocking doses of antipneumococcal rabbit serum. VI. Diminution of circulating pneumococcal polysaccharide. VII. Variations in reversed passive anaphylactogenic properties of different lots of antipneumococcal rabbit serum