1. Sixteen out of seventeen rabbits actively sensitized to various antigens by repeated cerebral and intravenous injections showed upon intracerebral reinjection of the same antigen local anaphylactic inflammation of the brain at the site of inoculation.
2. Six out of twenty rabbits actively sensitized to either horse serum or egg albumen by extracerebral injections, showed, upon introduction of the homologous antigen into the cerebrum, local anaphylactic inflammation at the site of inoculation.
3. The pathological picture of the Arthus phenomenon in the brain of the rabbit resembled that seen in the skin, after allowing for differences in the fundamental structure of the tissues involved.
4. None of the control animals exhibited lesions comparable to those found in the experimental animals. A few controls showed slight hemorrhages due to mechanical injury of blood vessels.
5. Clinical symptoms of varying degrees of severity, often leading to the death of the rabbit were observed in the sensitized animals. These symptoms were referable to the site of injection.