The valves shown in the accompanying drawing were designed primarily for use in preventing the waste of volatile anesthetics that commonly occurs in mammalian experiments when a Wollf's bottle is used in connection with a trachea tube and for simplifying the measurement of expired air in such experiments. Construction of plated brass with valve discs of aluminum, or of aluminum throughout, is satisfactory. An average of results from a test made on an 8 Kg. dog during a period of four hours is given below. The valves were not observed to stick or miss catching throughout the experiment.
1. Animal with tube in trachea breathing through a Wollf's bottle arrangement. Valves connected on the far side of the bottle in order to measure the volume of expired air. Volume of air measured by conveying it through a tube from the side branch to a spirometer.
2. Same arrangement as in