The steady state of heat production of nerve

At rest at 20°C. in oxygen a frog's nerve produces heat at a rate of about 70 X 10-6 cal./gm. sec. (Beresina, 1932). All activity is superimposed upon this “basal” state. If a nerve be stimulated at not too high a frequency its rate of heat production rises, until in 25 to 40 minuted (at 20°C.) it reaches a steady level in excess of the “basal.” If the stimulus be then stopped the rate of heat production gradually returns to its initial “basal” value. The process is illustrated in fig. 1. The frequency was low (9∙7 shocks per second) and the final value reached by the extra heat production after 35 minutes stimulation was 9∙7 X 10-6 cal./gm. sec. or 10-6 cal./gm. impulse. In fig. 1 galvanometer deflection is given without analysis: the latter would make the curve rise and fall rather more sharply at the beginning and end of stimulation. Fig. 2 gives such analyses, in 5-second units without remainders. Of these, (A) is of the beginning of stimulation, (B) of the end. The heat production in (B) is negative—just as (A) represents the sudden change up-wards from the basal rate at the beginning of stimulation, so (B) represents the sudden change downwards at the end of stimulation from the steady level during stimulation.