Electrical training and biological objects
Trained in physics and electrical methods at Oberlin and Cornell, Cole investigated sea urchin eggs at Woods Hole in 1924. He subsequently measured electrical properties of eggs, algae and nerve cells, using alternating-current bridges to make membrane resistance and capacitance experimentally comparable.
References: [1]
Resistance falls while capacitance changes little
In 1938 Cole and Curtis demonstrated a large fall in membrane resistance during excitation in Nitella and squid giant axons, with little change in capacitance. This helped distinguish changes in electrical pathways through a membrane from wholesale disruption of its basic structure.
References: [1]
Controlling membrane voltage by feedback
After the war, Marmont built internal axon electrodes and feedback equipment at Cole’s institute. Cole proposed a mode that controlled current according to membrane voltage. Early experiments in 1947 held voltage at selected levels while measuring current, establishing a technical route toward separating ionic currents.
Apparatus limitations and later improvements
Electrode polarization and uneven voltage along an axon could distort measurements. Cole later worked with John Moore and others to improve apparatus and analyze such errors. He established a biophysics laboratory at NIH in 1959 and published Membranes, Ions and Impulses in 1968.
References: [1]