CHEMICAL CHANGES IN THE ADDUCTOR MUSCLE OF THE CHELIPED OF THE CRAYFISH IN RELATION TO THE DOUBLE MOTOR INNERVATION

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Abstract
An investigation has been made of the phosphate and lactic acid changes in the adductor muscle of the cheliped of the crayfish Cambarus clarkii upon stimulation of the isolated axons for the fast and slow contractions at determined frequencies. When the mechanical effects of the 2 types of contraction were the same, the chemical changes were of the same order. If the mechanical effects were different, the chemical changes were not equivalent. This is especially to be seen in the case of stimulation at 50 shocks per sec: a slowly rising, long continued, strong slow contraction takes place with no apparent change in the phosphate content; a quickly rising fast contraction occurs with a large increase in phosphate. Since equivalent chemical changes accompany equivalent mechanical action, the 2 types of contraction do not differ in the essential mechanism of the chemical changes involved, and only one type of contractile substance is present. Even when a contraction has taken place to the maximum extent obtainable, only enough phosphate is found to correspond to 1/5 to 1/3 of the available phosphagen.