The Schultz--Dale reaction of the depolarized guinea-pig uterus.

1. The sensitized guinea-pig uterus contracted on addition of antigen (egg-albumin), even after it had been completely depolarized in an isotonic potassium sulphate solution.2. The contractile response of the depolarized preparation started at a later time after addition of the antigen, and had a smaller amplitude, than the Schultz-Dale contraction induced in the ordinary Ringer solution.3. A contracting substance was released from the depolarized uterus. The average histamine equivalent of this substance was 89% of the histamine concentration which reproduced the anaphylactic contraction and probably proportional to the mechanical response.4. The main component of the material released from the uterus in the ordinary Ringer was histamine. The material released from the depolarized uterus did not contain any demonstrable histamine activity.