The possession of concentrated light led to the discovery of the exact
mode in which the brain acts in the living man. By experiments on
transparent fish of the zoophyte class, and on the eyes of animals, we
discovered the means of making a living body for a time transparent. The
skull was rendered transparent accordingly, and by the aid of
concentrated light and of an instrument called an "electric viewer," the
currents of electricity in the brain were made visible.
These currents include myriads of electrical lines--literally composed
of electricity--lines the nearest approach to your definition of a
mathematical line, that which hath length without breadth.
The filaments, as we may truly call them, are of different forms,
straight, spiral, and otherwise curved, and of varied length and
colours. They are set in motion by the impulsion of thought. When we
talked to the patient on a particular subject, one series of lines would
be set in motion with indescribable rapidity; other topics would call
into play other series of straight or curved lines. They can also be set
in motion under the influence of certain electricities.
Although the experiments on the living man proved very valuable, they
could not be conducted with impunity, and were therefore not often
repeated. The man operated upon was insensible for some time afterwards,
and felt the effects for years. He was, however, cared for during the
rest of his life, and was not expected to work. Moreover, every kind of
comfort, luxury, and amusement was provided for him and for a certain
number of relatives and friends whom he selected as companions. Still he
was not allowed to marry, that being one of the principal conditions to
which he subscribed on being chosen for the experiment from amongst a
host of candidates to whom all the serious consequences attending the
operation were made known.