. The student of industrial efficiency is, for
instance, constantly led to the question of fatigue. He may consider
this fatigue as a function of brain and muscle activity and discuss it
with reference to the psychophysical effort, but he is equally
interested in the question of how far the apparatus or the machine or
the accessory conditions of the work might be changed in order to
avoid fatigue. The accidents of the electric street railways were
regarded as partly related to fatigue. The problem was accordingly how
to shorten the working time of the motormen in the interest of the
public, but it was soon recognized that the difficulty might also be
approached from the mere technical side. Some companies introduced
seats which the motormen can use whenever they feel fatigue coming and
excellent results have followed this innovation. In our last
discussions the technical apparatus stood in the foreground. We may
now consider as our real topic the psychophysical activity.

Here, too, the leaders of scientific management have secured some
signal successes. Their chief effort in this field was directed toward
the greatest possible achievement by eliminating all superfluous
movements and by training in those movement combinations which were
recognized as the most serviceable ones. We may return to the case of
the masons in order to clear up the principle. When Gilbreth began to
reform the labor of the mason after scientific principles, he gave his
chief interest to the men's motions. Every muscle contraction which
was needed to move the brick from the pile in the yard to the final
position in the wall was measured with reference to space-and
time-relations and the necessary effort. From here he turned to the
application of well-known psychophysical principles. A movement is
less fatiguing and therefore economically most profitable if it occurs
in a direction in which the greatest possible use of gravitation can
be made If both hands have to act at the same time, the labor can be
carried out most quickly and with the smallest effort if corresponding
muscle groups are at work and this means if symmetrical movements are
performed. If unequal movements have to be made simultaneously, the
effort will become smaller if they are psychically bound together by a
common unified impulse. The distance which has to be overcome by
hands, arms, or feet must be brought to a minimum for each partial
movement. Most important, however, is thi