1. Plain broth is just as effective as specific broth filtrate if used as a skin compress for the protection of guinea pigs against a subcutaneous injection of Staphylococcus aureus.
2. Plain broth compresses applied for 48 hours previous to bacterial injection sometimes prevent the death of the animal and practically always alter the inflammatory reactions.
3. This protection is not specific and is localized to the area "compressed."
4. The protection lasts at least 24 hours after removal of the compress.
5. Broth compresses applied to the abdominal wall of a guinea pig for 48 hours produced definite histological changes, especially in the subcutis, i.e., edema, proliferation of clasmatocytes, thickening of the epidermis together with a moderate exudation of polymorphonuclears and small mononuclear cells.
6. The histological response to the subcutaneous injection of staphylococci was different in the control and the broth-prepared animal.
7. In the broth-prepared animal, there was an increase in clasmatocytes and fibroblasts with a dense exudation of polymorphonuclears, which latter, in the main, did not degenerate. The clasmatocytes phagocyted bacteria early and later engulfed the polymorphonuclears, while the fibroblasts rapidly walled off the lesion. The result was a localized abscess which either came to the surface and ruptured or was absorbed and organized.