1. The eosinophilic response of the guinea pig sensitized and reinjected with the specific antigen varies with the nature of the antigen used, but also with the individual guinea pig in any groupsensitized and reinjected with the same antigen.
2. Certain antihistamine drugs which abolish anaphylactic symptoms, do not abolish the eosinophilic response.
3. The severity of anaphylactic "shock" symptoms has no influence on the eosinophilic response.
4. Histamine phosphate has no effect on the eosinophil count of nonsensitized guinea pigs protected by benadryl; it causes a distinct eosinophilic response in sensitized animals.
5. Heparin—in the dose injected—produced only an insignificant rise in the peripheral eosinophil count of sensitized guinea pigs; adenosine had no effect.
6. Attempts were made to correlate the eosinophilic response in bone marrow, blood and shock tissue of guinea pigs sensitized and reinjected with a specific antigen. The variation within a wide range of the number of eosinophils in the bone marrow of nonsensitized and of sensitized, reinjected guinea pigs is emphasized. A definite correlation seems to exist between the presence of a large number of eosinophils in blood and lungs; it is shown, however, that this observation permits only limited conclusions.
7. The factors which account for discrepancies in the interpretation of the eosinophilic response, e.g., nature of antigen, route of administration and characteristics of species, are analyzed.
8. The significance of the findings is reviewed in the light of previous work.
ACKNOWLEDGMENT We wish to express our appreciation to Miss Alice Sprenger for her patient and efficient technical assistance.