Studies in Asthma

1. Sheep serum in doses below 0.3 cc. intravenously produces no pulmonary vasoconstriction in the guinea pig. Guinea pigs have consequently been sensitized with this substance and anaphylactic shock produced by doses of O.1 and 0.2 cc. 2. Pressure in the pulmonary artery has been measured by the method of Drinker and Went (2) and recorded photographically in a new and convenient manner. 3. At a very early stage in anaphylactic shock the pulmonary arterial pressure falls markedly and this fall seems to precede the appearance of bronchiolar obstruction. 4. The fall in pulmonary blood pressure in anaphylactic shock is in marked contrast to the rise in pressure resulting from intravenous injection of toxic foreign protein, such as horse serum.