Calorimetry of Small Animals and Some Consequences of the Thermodynamics of Irreversible Processes

Abstract

Microcalorimetric experiments have been performed on several small animals with length up to 30 mm. The thermograms show in all cases strong fluctuations and regular patterns which are due to locomotor activities, to changes in the metabolism or to developmental metamorphoses. Heat production is compared to oxygen consumption which is determined after the calorimetric experiment in a Warburg apparatus or simultaneously with an IC pressure transducer adapted to the calorimetric vessel.

The specific rates of metabolism are calculated from these data and evaluated as functions of dry and wet weight. These functions exhibit the expected parabolic slope with exponents ranging from a pure surface to a volume dependence. Specific entropy production — taken as dissipation of heat -decreases during the development of an animal towards a minimum value. Some considerations concerning the difference between the heat production measured calorimetrically and that calculated from oxygen consumption are presented and discussed in connection with the thermodynamics of irreversible processes.