endency 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.

FECHNER EXPOUNDS WEBER'S LAW

The chief purport of this classical book of the German
psycho-physiologist was the elaboration and explication of experiments
based on a method introduced more than twenty years earlier by his
countryman E. H. Weber, but which hitherto had failed to attract the
attention it deserved. The method consisted of the measurement and
analysis of the definite relation existing between external stimuli
of varying degrees of intensity (various sounds, for example) and the
mental states they induce. Weber's experiments grew out of the familiar
observation that the nicety of our discriminations of various sounds,
weights, or visual images depends upon the magnitude of each particular
cause of a sensation in its relation with other similar causes. Thus,
for example, we cannot see the stars in the daytime, though they shine
as brightly then as at night. Again, we seldom notice the ticking of a
clock in the daytime, though it may become almost painfully audible in
the silence of the night. Yet again, the difference between an ounce
weight and a two-ounce weight is clearly enough appreciable when we
lift the two, but one cannot discriminate in the same way between a
five-pound weight and a weight of one ounce over five pounds.

This last example, and similar ones for the other senses, gave Weber
the clew to his novel experiments. Reflection upon every-day experiences
made it clear to him that whenever we consider two visual sensations, or
two auditory sensations, or two sensations of weight, in comparison
one with another, there is always a limit to the keennes