Abstract: An apparatus was devised for recording the changes of the course of "asthma" in guinea pigs produced by atomized histamine, instead of observing the same course by vision. It gives a characteristic figure of the respiratory changes that illustrate the extreme asphyxia of the animal. Drugs effective in causing bronchodilation may eliminate or modify the characteristic respiratory figure by virtue of the relief of bronchospasm produced by histamine. The method provides a more objective criterion for evaluating the antiasthmatic action of bronchodilators in animals.