not occur. Szent-Gyorgyi's suggestions (which were immeasurably strengthened by the new
knowledge) were well received by the main body of biological science, and the solid-state physicists
were reluctant to enter the messy, complex, biological world. Their investigations were limited to the
study of electronic processes in ultra-pure crystals of organic chemicals such as anthracene. Most
ironically of all, Szent-Gyorgyi's ideas seem to have been ignored by the few biological scientists who
persisted in studying bioelectrical phenomena (3,4).
The Nervous System
Not all neurophysiologists were convinced that the simple nerve impulse or action potential was
the sole basis of all nervous system function. While it could not be questioned that this mechanism did
exist and did furnish an adequate basis for the transmission of information in a single neurone, many
problems remained unanswered. Most important was the question of how all of the neurones integrated
and worked together to produce a coherent functioning brain (perhaps the whole was greater than the
sum of the parts). While most basic scientists avoided such questions, the clinical neurologists were
convinced that something was lacking in the action potential only concept.
In the 1940's Gerard and Libet reported a particularly significant series of experiments on the
DC electrical potentials measurable in the brain. (5)
.
Fig. 2.1. Schematic representation of a typical single neurone layer of cells in the frog brain used by
Libet and Gerard to measure DC electrical gradients. Their concept of the DC gradient along a single
neurone is shown in the lower figure. It is likely that the polarity was the result of the neurone being
removed from the brain as the polarity of the neurone intact and in the nervous system is opposite to
what they found.
In frogs, for example, some areas of the brain are only one neurone thick but are composed of
many such neurones oriented all in one direction. In such areas steady or slowly varying potentials
oriented along the axonodendritic axis were measured. These potentials changed in magnitude as the
excitability level of the neurones was altered by chemical treatment. In other experiments using
isolated but living frog brains, they found slowly oscillating potentials and "traveling waves" of
potential change moving across the cortical layers of the brain at speeds of approximately 6 cm per
second. These waves (which could be elicited by the application of a number of drugs, such as caffeine,
that increased the excitability of the individual neurones) had some very important properties. If a cut
was made on the cortical surface and the edges separated, the traveling wave could not cross the cut.
ELECTROMAGNETISM & LIFE - 22