The changes in the levels of total anthrone positive substances glycogen and glucose and the activities of phosphorylase, lactate dehydrogenase and succinate dehydrogenase were studied in thein situ heart of the scorpionH. fulvipes, based on the theme of acceleration and inhibition. TAPS and glucose showed appreciable depletion in the accelerated hearts and conservation in the inhibited hearts. Glycogen depletion in the accelerated hearts is not significant while conservation in the inhibited hearts is significant. Both active and total phosphorylases as well as the combined ratio showed increasing trend with increase in heart rate andvice versa. The role of carbohydrates as metabolic fuel to sustain the heart beat is also discussed.