hat
the astronomer Bessel had noted a half-century before. It was found,
too, that the rate of activity varies also for the same person under
different conditions, becoming retarded, for example, under influence of
fatigue, or in case of certain diseases of the brain. All details aside,
the essential fact emerges, as an experimental demonstration, that the
intellectual processes--sensation, apperception, volition--are linked
irrevocably with the activities of the central nervous tissues, and
that these activities, like all other physical processes, have a time
element. To that old school of psychologists, who scarcely cared more
for the human head than for the heels--being interested only in the
mind--such a linking of mind and body as was thus demonstrated was
naturally disquieting. But whatever the inferences, there was no
escaping the facts.

Of course this new movement has not been confined to Germany. Indeed,
it had long had exponents elsewhere. Thus in England, a full century
earlier, Dr. Hartley had championed the theory of the close and
indissoluble dependence of the mind upon the brain, and formulated
a famous vibration theory of association that still merits careful
consideration. Then, too, in France, at the beginning of the century,
there was Dr. Cabanis with his tangible, if crudely phrased, doctrine
that the brain digests impressions and secretes thought as the stomach
digests food and the liver secretes bile. Moreover, Herbert Spencer's
Principles of Psychology, with its avowed co-ordination of mind and body
and its vitalizing theory of evolution, appeared in 1855, half a
decade before the work of Fechner. But these influences, though of vast
educational value, were theoretical rather than demonstrative, and the
fact remains that the experimental work which first attempted to gauge
mental operations by physical principles was mainly done in Germany.
Wundt's Physiological Psychology, with its full preliminary descriptions
of the anatomy of the nervous system, gave tangible expression to the
growth of the new movement in 1874; and four years later, with the
opening of his laboratory of physiological psychology at the University
of Leipzig, the new psychology may be said to have gained a permanent
foothold and to have forced itself into official recognition. From then
on its conquest of the world was but a matter of time.

It should be noted, however, that there is one other method of strictly
experimental