bit and volition,
distraction and fatigue. Here subtle methods have been elaborated,
methods which surely common sense cannot supply, and which showed
differences of mental behavior with the exactitude with which the
microscope reveals the hidden differences of form. If physicians are
slow in accepting the help which the psychological laboratory can
furnish, it may be in good harmony with the desirable conservative
policy in medicine, but finally the time must come when this
instinctive resistance against new methods will be overcome. The recent
attachment of psychological laboratories to certain leading psychiatric
clinics is a most promising symptom. Yet the diagnostic studies with the
means of the psychological laboratory cannot be confined to the cases of
mental disease. The mild abnormalities of the mind, and especially the
nervous disturbances which exist outside the field of insanity, demand
this support of psychology much more. And even the normal personality
will be more safely protected from disease and from social dangers for
its mental constitution if the resources of experimental psychology are
employed. The more we know of the psychological constitution of the
individual, the more we can foresee the development which is to be hoped
for or feared and which may be encouraged or retarded.

The psychologist may determine, for instance, the degree of attention
with its resistance against distracting stimuli, the power of memory
under various conditions and on various material, the mental
excitability and power of discrimination, the quickness and correctness
of perception, the chains of associations, the rapidity of the
associative process for various groups, the types of reaction, the
forming of habits and their persistence, the conditions of fatigue and
of exhaustion, the emotional expressions and the emotional stability,
the time needed for recreation and the resistance against drugs, the
degree of suggestibility and the power of inhibition: and every result
in any of these lines may contribute to the diagnosis and prognosis of
cases. The chronoscope here measures the reaction times and association
times in thousandths of a second; the kymograph, by the help of the
sphygmograph, writes the record of the pulse and its changes in
emotional states, while the pneumograph records the variations of
breathing, and the plethysmograph shows the changes in the filling of
blood vessels in the limbs which is immediately