462 HYPNOTISM.
Nevertheless, such errors recur occasionally. Just as Berillon did formerly,
so Grasset in the present day still believes that hemi-hypnosis proves that
the two cerebral hemispheres act independently. This is but an instance of the
kind of exaggeration met with in every domain of research (cf. p. 87). Similarly,
the theory of the Double-Ego has nothing to do with any disturbance in the equilibrium
of the two cerebral hemispheres, as some assume to be the case. Krauss, in his
biography of Ribot, lays stress on the fact that the latter has refuted this
theoretical deduction. There are individuals who think they possess a triple
personality ; thus, a priest got himself so involved in the mystery of the Trinity
that. he believed himself to be three distinct persons, and wanted three places
laid for him at table. Here we see the above-mentioned physiological interpretation
of hypo-consciousness carried at
once ad absurdum.
Hypnotism has, nevertheless, had its influence on physiology, if only more in
a negative way, in that physiological explanations have had to give way to psychological
ones. At the same time, it must certainly be admitted that psychical influences
are ultimately physiological processes, only we are to-day so far off any possible
means of explaining this, that it is better to keep our conception of them untrammelled
by physiology. In former times the.possibility of explaining such states as
sleep by means of chemical and physical theories was often exaggerated. Nevertheless,
it is impossible to establish a satisfactory theory of sleep without taking
psychology, and suggestion in particular, into consideration. This is not to
be taken to mean that we look upon sleep itself as a phenomenon of auto-suggestion—a
view to which some people incline—but that the psychological factors must
invariably be considered in conjunction with the physiological; both play a
part. The fact that excitement will banish the severest symptoms of fatigue
instantaneously, discloses the psychological factor; and the fact that sleep
becomes a necessity after a long vigil probably has a physiological explanation.
It is the same with muscular fatigue. Vignolle has recently published a work
on fatigue, in which he very properly separates the subjective moment in the
production of fatigue from the objective. Even if muscular fatigue is brought
about by chemical and physical changes, it is, nevertheless, greatly influenced
by psychical processes. The thought of soon getting tired may
HYPNOSIS AND PSYCHOLOGY. 463