RESPIRATORY MOVEMENTS AND ENDURANCE OF FROGS AT LOW PRESSURES

Abstract

Exposure of three species of frogs (Rana pipiens, R. clamitans, and R. sylvatica) to pressures of 1.5, 3.0, and 5.0 cm. Hg induces characteristic changes in the frequency and type of breathing. The immediate initial effect is that of increasing both mouth and lung oscillations for a brief period, prior to a gradual decline in rate. Lung oscillations persist longer than mouth oscillations, and on return to normal atmospheric pressure, are initiated earlier and at a rapid rate. During advanced stages of decompression, excess lung inflation is resultant from several consecutive inhalations, prior to a deep exhalation. R. pipiens is most resistant to low pressure, and R. sylvatica least resistant. Large individuals of a species survive longer than small. Survival is better with little oxygen in an atmosphere of nitrogen at normal atmospheric pressure than with a comparable oxygen supply at a reduced pressure. A brief acclimatization to pressures of 1.5 and 3.0 cm. Hg can be produced by prolonged exposure to 15 cm. Hg but not by intermittent exposures to low pressure.