Electrical resistance, conductivity and permeability as measures of injury and recovery

Child, in Individuality in Organisms (1915), treated the conductivity of protoplasm as something an experimenter could change. He noted that reproduction can be induced in plants and many lower animals by isolating pieces. In such pieces it is often possible to increase or decrease dominance and so to extend or shorten its range. Child listed the alteration of conductivity beside the elimination of old metabolic gradients and the setting up of new ones as ways to control individuation to some extent.¹ The passage gives no numerical values. It presents conductivity as one of several controllable conditions, not as a measured quantity.

Osterhout, in Injury, Recovery and Death in Relation to Conductivity and Permeability (1922), reported curves of net electrical resistance for Laminaria agardhii. One figure shows tissue in NaCl 0.52 M, in CaCl2 0.278 M and in sea water, with calculated values as unbroken lines and observed values as broken lines. The curves are averages of ten or more experiments, with a probable error of the mean under 10 percent.² Another figure follows resistance falling in a mixture of 97.56 mols of NaCl to 2.44 mols of CaCl2, then recovery in sea water after different exposure times.⁴ For the calculation of recovery, the value of A reached after 60.6 minutes in NaCl is substituted in formula (7).³

Lillie, in Protoplasmic Action and Nervous Action (1923), named the electrical conductivity of protoplasm and medium, and the electrical polarization of the plasma membranes, as general physical conditions that depend on salts.⁵ He held them important for the normal activity of protoplasm and deferred them to his later treatment of stimulation.⁵ On the three chief cations, Na, K and Ca, he wrote that their relations to protoplasmic activity depend on chemical conditions still imperfectly understood. Na and K act as physiological antagonists in vertebrate muscle, he said, while in other protoplasm, such as fish and sea-urchin eggs, the differences are relatively slight.⁶

Child, in Physiological Foundations of Behavior (1924), tied conductivity to the range of physiological dominance. He described dominance as an excitatory and transmissive relation. Excitation usually declines in effectiveness with distance until it fails, so range is limited by the decrement in transmission. On this account the range is very short in early embryonic stages, where the conductivity of protoplasm for excitation is rather low, and it increases during development.⁷ In vertebrate nerves Child called it certainly very great, and noted that many regard it as unlimited. He added that experiment showed range varying with the metabolic rate of the dominant region, falling as the rate falls.⁸