Comparative physiology of lung surfactants : five amphibians and a representative mammal

Lung washings from five amphibian species were tested for the presence of surfactants by the capillary method, All had high surface tensions, insignificantly different from that of the Ringer's solution used for the lung washing. In contrast, lung washings from rats showed a significantly lower surface tension. Comparison with solutions of known concentrations of lecithin showed the washings to be very dilute, about 10⁻⁵ g/l. Possibly, if the lung washings were concentrated, and time enough allowed for the surface film to equilibrate, the surface tension would be lower.