The Song of the Cell: An Exploration of Medicine and the New Human

by Siddhartha Mukherjee

saw the arrival of a small electrical impulse—a mini wave—followed by a large wave of charged ions moving into the neuron. The large wave subsided, and dipped, and then the system was reset to normal. Again and again, when they stimulated the axon, they saw the same rising spike of charge, and its restoration to normal. They had observed the dynamics of a nerve conducting its signal to another nerve. The war interrupted Hodgkin and Huxley’s collaboration for nearly seven years. Hodgkin, the engineer-tinker, was sent off to make oxygen masks and radars for pilots; Huxley, the mathematician, was deployed to use equations to make machine guns more accurate. In 1945, shortly after the war ended, they resumed their work in Plymouth, scouring the catch for squid and delving deeper and deeper into the nervous system, finding more accurate ways to measure the flow of charge into the neuron, culminating in a mathematical model to describe the movement of ions into the neuronal cell. Nearly seven decades later, neuroscientists are still using the Hodgkin and Huxley equations, and their experimental methods, to understand the nervous system. The broad outlines of how a neuron “chatters” are now understood. Perhaps we can turn to one of Cajal’s drawings as a template to elucidate the movement of a signal through a nerve. Imagine the nerve, first, in its “resting” state. At rest, the internal milieu of the neuron contains a high concentration of potassium ions and a minimal concentrati...