tioning mainly of that part of the individual's organization con-
nected with the use of the large muscles of the body. When we
need a short phrase we characterize it simply as manual work.
To use the term manual in this broad way is, of course, to strip
it of its etymological setting. When the individual is multi-
plying or adding or planning the details of a lecture the process
involves mainly that part of his organization connected with the
small muscles employed in using words. Short characterizing
phrases are subvocal work or vocal work, depending upon whether
the work is done silently (thought) or spoken aloud. But neither
in manual work nor in implicit laryngeal work does action take
place only in the specified parts. The manual worker may be
thinking of his family or of the nearness of meal-time, whereas
the laryngeal worker may be tearing his hair or walking up and
down the room. (2) The attempt is made to literally drag in
by the hair pictures of what goes on in the nervous system and
the muscles. Thorndike, who in general stays closest to investi-
gatable grounds, defines "mental work" as work done by the
animal's connection system. "When, however, such a total activ-
ity is examined more critically, it is found desirable to separate
off the work and fatigue of the sense organ and of the end plate
in the muscle from the work of the connection system and to
distinguish sensorial fatigue, intellectual fatigue and muscular
fatigue. For the action of a sense organ or of an end plate is
only partly, and the action of a muscle fiber is not at all, like
that of the connecting neurone." He passes into the realm of
classification of fatigue with a vengeance in the following note:

"It will doubtless be better in the long run to subdivide the
work of the human animal still further and to replace the terms
sensory, mental and muscular work by the work of the accessory
apparatus of the sense organs, the work of the peripheral end
of the first sensory neurone, the work of conduction along a neu-
rone, the work of conduction across a synapse from neurone to
neurone, the work of changing the intimacy of synapses, the
work of conduction from the ending of a neurone to a muscle,
the work of the muscle fibers." (Italics in text omitted.)

(3) The final factor which has brought the psychology of

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