||The work of the
nerve physiologists had thus an important bearing on questions of the mind.
But there was another company of workers of this period who made an even
more direct assault upon the "citadel of thought." A remarkable school
of workers had been developed in Germany, the leaders being men who, having
more or less of innate metaphysical bias as a national birthright, had
also the instincts of the empirical scientist, and whose educational equipment
included a profound knowledge not alone of physiology and psychology, but
of physics and mathematics as well. These men undertook the novel task
of interrogating the relations of body and mind from the standpoint of
physics. They sought to apply the vernier and the balance, as far as might
be, to the intangible processes of mind.
The movement had its precursory stages
in the early part of the century, notably in the mathematical psychology
of Herbart, but its first definite output to attract general attention
came from the master-hand of Hermann Helmholtz in 1851. It consisted of
the accurate measurement of the speed of transit of a nervous impulse along
a nerve tract. To make such measurement had been regarded as impossible,
it being supposed that the flight of the nervous impulse was practically
instantaneous. But Helmholtz readily demonstrated the contrary, showing
that the nerve cord is a relatively sluggish message-bearer. According
to his experiments, first performed upon the frog, the nervous "current"
travels less than one hundred feet per second. Other experiments performed
soon afterwards by Helmholtz himself, and by various followers, chief among
whom was Du Bois-Reymond, modified somewhat the exact figures at first
obtained, but did not change the general bearings of the early results.
Thus the nervous impulse was shown to be something far different, as regards
speed of transit, at any rate, from the electric current to which it had
been so often likened. An electric current would flash halfway round the
globe while a nervous impulse could travel the length of the human body
- from a man's foot to his brain.
The tendency to bridge the gulf that hitherto
had separated the physical from the psychical world was further evidenced
in the following decade by Helmholtz's remarkable but highly technical
study of the sensations of sound and of color in connection with their
physical causes, in the course of which he revived the doctrine of color
vision which that other great physiologist and physicist, Thomas Young,
had advanced half a century before. The same tendency was further evidenced
by the appearance, in 1852, of Dr. Hermann Lotze's famous Medizinische
Psychologie, oder Physiologie der Seele, with its challenge of the old
myth of a "vital force." But the most definite expression of the new movement
was signalized in 1860, when Gustav Fechner published his classical work
called Psychophysik. That title introduced a new word into the vocabulary
of science. Fechner explained it by saying, "I mean by psychophysics an
exact theory of the relation between spirit and body, and, in a general
way, between the physical and the psychic worlds." The title became famous
and the brunt of many a controversy. So also did another phrase which Fechner
introduced in the course of his book - the phrase "physiological psychology."
In making that happy collocation of words Fechner virtually christened
a new science.