The heat-production and recovery of crustacean nerve

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Abstract
In a recent paper Furusawa (1) has shown that the “retention of action current” described by Levin (2) as occurring in the stimulated limb or claw nerve of a crab or lobster is to be regarded as a “depolarisation” of the nerve, in the sense that the electrical potential difference normally present in the living nerve fiber, existing presumably across its boundary, is gradually discharged by stimulation. This potential difference is the cause of the phenomenon commonly known as the “injury current,” which is found when two electrodes placed upon the injured surface and a cut end respectively are connected to a galvenometer. In the presence of oxygen the “retention of action current” slowly disappears; the potential difference gradually rises again in the course of half-an-hour or so (depending on the temperature and the duration of the stimulation) to its original value; in the absence of oxygen the nerve remains “discharged.” Furthermore, if a resting nerve be deprived of oxygen the potential difference slowly falls, but rises again if oxygen be readmitted. It is difficult to resist the conclusion that the potential difference normally existing is maintained by oxidative processes in the nerve, and that it is restored, after stimulation, by some kind of “galvanic combustion element,” as suggested by Straub (3) to explain the difference of osmotic pressure found between the yolk and the white of a living hen’s egg. No chemical changes are known with certainty to occur during the initial phase of nerve activity,i. e., during the transmission of the impulse; according to Gerard and Meyerhof (4) stimulation of a nerve in nitrogen leads to no appreciable increase in the rate of lactic acid formation. Moreover, the heat-production during this first phase, judging from the case of frog’s nerve (5, 6) is very small, viz., only about 10 per cent. of the heat associated with the whole cycle (including recovery). Even in frog’s nerve, however, it is know that stimulation in the absence of oxygen causes more rapid failure than oxygen want alone. It may well be the case that the initial phase of activity is concerned primarily with some kind of physical process involving electromotive effects, such as would ensue if contact were momentarily permitted between two different electrolyte solutions. Such a mixing of electrolytes permitted to occur during the passage of each impulse would lead to a gradual “discharge” of the nerve but to very little heat-production; the separation of the electrolytes, however, after activity, would require a supply of free energy in any actual working process, and probably a considerable liberation of heat.

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