In the studies by Plotz, Olitsky, and Baehr! on the etiology of typhus fever, one of us reported the occurrence of agglutinins, complement-fixing bodies, precipitins, and opsonins in the blood of typhusfever patients. It is significant that all types of antibodies occurred regularly after the crisis, occasionally at the crisis, and only rarely before the crisis. These antibodies usually persisted in the blood many months after convalescence. In the blood of the guinea-pig, to which the disease

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... s transmitted by the injection of human virus, no antibodies except opsonins could be demonstrated. The present paper is concerned with the study of the serum of patients and of guinea-pigs suffering or recovering from typhus fever, by a method involving the anaphylactic· response. This method was first used by Dale" in the study of anaphylactic phenomena. It depends on the muscular contraction of the uterus of a sensitized guinea-pig when brought in contact with the antigen. Briefly, the technic of all such experiments is as follows: The uterus is removed from the animal and suspended in a container filled with Locke's solution, kept at a temperature of 37-40 C.; it is attached to a lever which writes on a moving drum. The antigen is added to the Locke's fluid bathing the uterus, and a contraction is recorded by the up-stroke of the lever. Ergamine is used to test the contractility of the muscle. This method was first successfully applied to the study of infectious diseases (pneumonia) by W eil. 3 Antigens prepared by various methods were tried. The following proved the most satisfactory. The 7-day anaerobic growth on 0.5% glucose serum agar of Bacillus typhi-exanthematici was emulsified in physiologic salt solution, * Received for publication October 12, 1916. Work done under tenure of George Blumenthal Jr.. fellowships in pathology.