THE EFFECT OF FATIGUE ON HEAT RIGOR AND CHLOROFORM RIGOR IN THE GASTROCNEMIUS AND SARTORIUS MUSCLES OF THE FROG

Abstract

Fatigued excised gas-trocnemius and sartorius muscles of the frog were found to shorten less than their unfatigued mates in heat rigor and in chloroform rigor. In the case of heat rigor the shortening began at a lower temperature following fatigue. No recovery either in ability to begin rigor at the temp. normal for unfatigued muscles or in the extent of shortening was indicated when fatigued muscles were left standing in air, but in pure O a marked recovery in both respects was obtained. When muscles were completely fatigued in CO2 or in N, the extent of rigor shortening was not lessened so much as when the fatiguing process was carried out in air, but the temp. at which rigor began was then lower, on the average, than in case of muscles fatigued in air. Tension developed under isometric conditions was studied in case of chloroform rigor, and fatigued muscles developed less tension than their non-fatigued mates. In chloroform rigor muscles lost weight due to exudate squeezed from the muscle by the rigor contraction. The unfatigued muscles lost more weight thus than their fatigued mates. Quantitative results are given throughout the paper.