soon afterwards all the leaders everywhere.
The result was a practically unanimous confirmation of the Spanish
histologist's claims, and within a few months after his announcements
the old theory of union of nerve cells into an endless mesh-work was
completely discarded, and the theory of isolated nerve elements--the
theory of neurons, as it came to be called--was fully established in its
place.

As to how these isolated nerve cells functionate, Dr. Cajal gave the
clew from the very first, and his explanation has met with universal
approval.

In the modified view, the nerve cell retains its old position as the
storehouse of nervous energy. Each of the filaments jutting out from the
cell is held, as before, to be indeed a transmitter of impulses, but a
transmitter that operates intermittently, like a telephone wire that is
not always "connected," and, like that wire, the nerve fibril operates
by contact and not by continuity. Under proper stimulation the ends of
the fibrils reach out, come in contact with other end fibrils of other
cells, and conduct their destined impulse. Again they retract, and
communication ceases for the time between those particular cells.
Meantime, by a different arrangement of the various conductors,
different sets of cells are placed in communication, different
associations of nervous impulses induced, different trains of thought
engendered. Each fibril when retracted becomes a non-conductor, but when
extended and in contact with another fibril, or with the body of another
cell, it conducts its message as readily as a continuous filament could
do--precisely as in the case of an electric wire.

This conception, founded on a most tangible anatomical basis, enables
us to answer the question as to how ideas are isolated, and also, as Dr.
Cajal points out, throws new light on many other mental processes.
One can imagine, for example, by keeping in mind the flexible nerve
prolongations, how new trains of thought may be engendered through novel
associations of cells; how facility of thought or of action in certain
directions is acquired through the habitual making of certain nerve-cell
connections; how certain bits of knowledge may escape our memory and
refuse to be found for a time because of a temporary incapacity of the
nerve cells to make the proper connections, and so on indefinitely.

If one likens each nerve cell to a central telephone office, each of
its filamentous prolongations to a telep