ut the relation of the
psychological factor itself to the total disturbance may be of most
different character. If I diagnose or treat the fixed idea of a
psychasthenic, the psychological factor itself represents the
disturbance. On the other hand, if I study the pain sensations of a
patient who suffers from a disease of the spinal cord, then the
sensations themselves, the only psychological factor in the case, are
only indications of a disease which belongs to an entirely different
physical region; the mind itself is normal. Or, on the other hand, if I
try to educate a sufferer from locomotor ataxia to develop his walking
by building up in his mind new motor ideas to regulate his cooerdinated
movements, the mind again is entirely normal but the physician needs his
psychology on account of the influence which the mind has on the bodily
system. Again, we must insist that psychomedicine covers this whole
ground. Wherever a psychical factor enters into the calculations of the
physician either by reason of its own abnormality or by its relation as
effect or as cause to a diseased part of the body in the brain or
without, there we have a psychomedical task, and as far as it is
therapeutic, we have psychotherapy.

The psychodiagnostic research lies outside of the compass of our book,
but we cannot emphasize sufficiently the great importance which belongs
to that work. Moreover, just in the field of psychodiagnostics, the
methods of the modern experimental psychological laboratory are most
promising and successful. Let us not forget that we deal with such
psychological factors even when we test the functions of eye and ear and
skin and nose by examining the sensations and perceptions. The oculist
who analyzes the color sensations of a patient and the aurist who finds
defects in the hearing of the musical scale and discovers that certain
pitches cannot be discriminated, is certainly dealing, for diagnostic
purposes, with the material that the psychological laboratory has sifted
and studied. Even that sensation symptom which enters into so many
diseases, the sensation of pain, belongs certainly within the compass of
the psychologist and it is only to be regretted that the systematic
study of the pain sensations, mostly for evident practical reasons, has
been much neglected in the psychological laboratory.

The psychologists have been at work all the more eagerly in the fields
of association and memory, attention and emotion, ha