How to Use Your Mind | Page 9

composed of minute units of structure called nerve-cells or neurones. Each of these
looks like a string frayed out at both ends, with a bulge somewhere along its length. The
nervous system is made up of millions of these little cells packed together in various
combinations and distributed throughout the body. Some of the neurones are as long as
three feet; others measure but a fraction of an inch in length.
We do not know exactly how the mind, that part of us which feels, reasons and wills, is
connected with this mass of cells called the nervous system. We do know, however, that
every time anything occurs in the mind, there is a change in some part of the nervous
system. Applying this fact to study, it is obvious that when you are performing any of the
operations of study, memorizing foreign vocabularies, making arithmetical calculations,
reasoning out problems in geometry, you are making changes in your nervous system.
The question before us, then, is, What is the nature of these changes?
According to present knowledge, the action of the nervous system is best conceived as a
form of chemical change that spreads among the nerve-cells. We call this commotion the
nervous current. It is very rapid, moving faster than one hundred feet a second, and runs
along the cells in much the same way as a "spark runs along a train of gunpowder." It is
important to note that neurones never act singly; they always act in groups, the nervous
current passing from neurone to neurone. It is thought that the most important changes in
the nervous system do not occur within the individual neurones, but at the points where
they join with each other. This point of connection is called the synapse and although we
do not understand its exact nature, it may well be pictured as a valve that governs the
passage of the nervous current from neurone to neurone. At time of birth, most of the
valves are closed. Only a few are open, mainly those connected with the vegetative
processes such as breathing and digestion. But as the individual is played upon by the

objects of the environment, the valves open to the passage of the nervous current. With
increased use they become more and more permeable, and thus learning is the process of
making easier the passage of the nervous current from one neurone to another.
We shall secure further light upon the action of the nervous system if we examine some
of the properties belonging to nerve-cells. The first one is impressibility. Nerve-cells are
very sensitive to impressions from the outside. If you have ever had the dentist touch an
exposed nerve, you know how extreme this sensitivity is. Naturally such a property is
very important in education, for had we not the power to receive impressions from the
outside world we should not be able to acquire knowledge. We should not even be able to
perceive danger and remove ourselves from harm. "If we compare a man's body to a
building, calling the steel frame-work his skeleton and the furnace and power station his
digestive organs and lungs, the nervous system would include, with other things, the
thermometers, heat regulators, electric buttons, door-bells, valve-openers,--the parts of
the building, in short, which are specifically designed to respond to influences of the
environment." The second property of nerve-cells which is important in study is
conductivity. As soon as a neurone is stimulated at one end, it communicates its
excitement, by means of the nervous current, to the next neurone or to neighboring
neurones. Just as an electric current might pass along one wire, thence to another, and
along it to a third, so the nervous current passes from neurone to neurone. As might be
expected, the two functions of impressibility and conductivity are aided by such an
arrangement of the nerve-cells that the nervous current may pass over definitely laid
pathways. These systems of pathways will be described in a later paragraph.
The third property of nerve-cells which is important in study is modifiability. That is,
impressions made upon the nerve-cells are retained. Most living tissue is modifiable to
some extent. The features of the face are modifiable, and if one habitually assumes a
peevish expression, it becomes, after a time, permanently fixed. The nervous system,
however, possesses the power of modifiability to a marked degree, even a single
impression sufficing to make striking modification. This is very important in study, being
the basis for the retentive powers of the mind.
Having examined the action of the nervous system in its simplicity, we have now to
examine the ways in which the parts of the nervous system are combined. We shall be
helped if we keep to the conception of it as an aggregation