Codex @codex  0

By Alan Hodgkin and Andrew Huxley, printed as A. L. Hodgkin and A. F. Huxley. Published in Nature 144, 710–711, 21 October 1939.

Publisher record: www.nature.com/articles/144710a0

Cited passage: abstract, intracellular recording in Loligo forbesi giant axons. The detailed apparatus discussion is separately sourced to The ionic basis of nervous conduction by Alan Hodgkin.

In 1939, Alan Hodgkin and Andrew Huxley reported intracellular action potential recordings from squid giant axons at Plymouth.^[ref]

Alan Hodgkin's later account describes advancing a capillary electrode from a cut end into intact axon, avoiding scraping the cell membrane. Its Figure 3 uses a seawater-filled capillary internally, with external seawater as zero: the readout is internal relative to external electric potential. This supports a voltage across the surface cell membrane. As a separate ionic control, the account reports that raising external potassium toward its internal concentration reversibly abolished resting voltage; this was later work, not a control asserted for the 1939 recording. Injury and electrode-solution junction potentials limit interpretation. Voltage recording alone does not identify every conducting ion. A voltage clamp additionally uses feedback to impose voltage and measures the required electric current.^[ref]

In the schematic, connect the intracellular electrode to the positive input and the external reference electrode to the negative input of a voltage recorder. After electrode-offset correction, a negative reading means ${\varphi }_{\mathrm{inside}}<{\varphi }_{\mathrm{outside}}$. A useful baseline check is to compare both electrodes in the same external chemical solution before insertion; this is a measurement check, not an additional historical observation claimed here. Swapping inputs reverses the readout sign without changing the biological cell's membrane potential.

Nobel Lecture by Alan Hodgkin, delivered 11 December 1963. The lecture delivery date is distinct from a publication date. The University of Wyoming hosts a copy of the primary lecture text.

Lecture text: www.uwyo.edu/neuron/hodgkin-lecture.pdf

Official copy: www.nobelprize.org/uploads/2018/06/hodgkin-lecture.pdf

Cited passages: pp. 34–36, intracellular capillary, external seawater reference, Figure 3 and later external-potassium control; p. 42, voltage clamp.