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Standardized histomechanical measurements on isolated normal human lungs were performed at 5,20, and 35 °C (on one lung from 5–50 °C with 5°C steps). There was an increase of dynamical compliance with a mean of + 23 % between 5 and 35 °C. Total pulmonary resistance accordingly fell about -34 %. The differentiation of the components of total pulmonary resistance revealed a decrease of airways resistance of about -29%, but its share of total resistance was slightly increased. Alterations of tissue elasticity (including surface tension) and tissue viscance were found to be the most important changes. Density and viscosity of the air presumably can be neglected. The changes induced by temperature are (partly) reversible. There seems to exist an optimum of mechanical properties at physiological temperatures. No explanations can be offered concerning the controversial theories of the behaviour of surface tension versus tissue elasticity and changes of surfactant activity

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