ABSTRACT
The experiments described here were made in Brazil during 1953. Their primary purpose was to explore the properties of the muscle fibres of the locally available frog, Leptodactylus ocelatus, and to find out whether, in spite of the very different climate to which the animals are accustomed, their isolated muscles provide as convenient experimental preparations, and give similar results to those obtained, for instance, with the sartorius of European Rana temporaria. This was found to be the case, and in addition to repeating a number of established effects on Leptodactylus ocelatus, some new results obtained with changes in the ionic composition of the solution will be reported. Intracellular recording of resting and action potentials was used and the conditions were chosen so that the experiments could be compared with those made by other authors. In addition, an investigation of the effect of some of the variables upon the rate of extrusion of sodium from the muscle fibres was measured by radioactive tracer methods ; these results will be reported later.
