1. 1. During acute anaphylactic shock in the rabbit, there occurs a marked decrease in the blood-histamine, a lesser decrease in the plasma-histamine and a leucopenia.2. 2. There does not appear to be any correlation between these changes and the symptoms of anaphylaxis.3. 3. There is a decrease in the histamine-content of the lung and spleen of the rabbit following the production of anaphylactic shock.4. 4. In non-sensitized rabbits, there is little or no change in the histamine-content of the blood following the intravenous injection of horse serum. A leucopenia may occur. When egg albumin is injected intravenously, however, a decrease in both the blood-histamine and the white blood count occurs.5. 5. Histamine-shock in the rabbit is characterized by a moderate decrease in the histamine-content of the blood and a marked increase in the histamine-content of the plasma. A moderate leucopenia also occurs. These findings then differ from those which occur in anaphylactic shock in this species.6. 6. By superimposing anaphylaxis on histamine-shock in the rabbit, it may be shown that not only is the histamine-content of the blood diminished, but that there is also some mechanism for the removal of large amounts of histamine from the plasma. It is also shown that a sudden increase in the plasma-histamine may occur under these circumstances.
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