1. A method is described for measuring the relative impedance of living cells to diathermy currents.
2. The diathermy current penetrates the living cell, and heat production is intracellular as well as extracellular.
3. A small proportion of the impedance of living cells to the diathermy current seems not to lead to the production of heat.
4. Evidence is given that the addition of saponin produces an appreciable increase in the conductivity of an electrolyte. Its use is therefore contraindicated when electrical measurements are being made on biological material.
5. The currents used in diathermy behave as do high frequency currents of the pure sine wave form in respect to their passage through biological material.