n to the physiologic conditions. Lastly, the psychic
activity may be initial and productive of changes in the organism, or,
if these already exist, may augment and prolong them.

The most instructive instances are those indicated by very clear
manifestations and profound modifications of the bodily condition. Such
are the moments of inspiration or simply those of warmth from work which
arise in the form of sudden impulses.

The general fact of most importance consists of changes in the blood
circulation. Increase of intellectual activity means an increase of work
in the cortical cells, dependent on a congested, sometimes a temporarily
anaemic state. Hyperaemia seems rather the rule, but we also know that
slight anaemia increases cortical excitability. "Weak, contracted pulse;
pale, chilly skin; overheated head; brilliant, sunken, roving eyes,"
such is the classic, frequently quoted description of the physiological
state during creative labor. There are numerous inventors who, of their
own accord, have noted these changes--irregular pulse, in the case of
Lagrange; congestion of the head, in Beethoven, who made use of cold
douches to relieve it, etc. This elevation of the vital tone, this
nervous tension, translates itself also into motor form through
movements analogous to reflexes, without special end, mechanically
repeated and always the same in the same man--e.g., movement of the
feet, hands, fingers; whittling the table or the arms of a chair (as in
the case of Napoleon when he was elaborating a plan of campaign), etc.
It is a safety-valve for the excessive flow of nervous impulse, and it
is admitted that this method of expenditure is not useless for
preserving the understanding in all its clearness. In a word, increase
of the cerebral circulation is the formula covering the majority of
observations on this subject.

Does experimentation, strictly so called, teach us anything on this
point? Numerous and well-known physiological researches, especially
those of Mosso, show that all intellectual, and, most of all, emotional,
work, produces cerebral congestion; that the brain-volume increases, and
the volume of the peripheral organs diminishes. But that tells us
nothing particularly about the imagination, which is but a special case
under the rule. Latterly, indeed, it has been proposed to study
inventors by an objective method through the examination of their
several circulatory, respiratory, digestive apparatus; thei