634 
explain and limit, but as no one has spoken 
from their ranks a word from a layman may be 
of service. 
The handling of objects which have been 
preserved in a 4 % solution kills the outer 
cuticle and appears to have a paralyzing effect 
on the sub-cuticular nerve terminations. Re- 
peated use demoralizes the skin very badly. 
The vapor or minute drops arising in dissection 
from the objects manipulated is liable to cause 
serious affections of the eye. We have just 
heard from a recent colaborator of the museum 
who has narrowly escaped the loss of one eye, 
and is probably condemned for life to the use 
of glasses as a result of dissections of slugs 
preserved in formalin. Irritation of the mu- 
cous membrane of the air passages has proba- 
bly been observed by every one who has used 
this preservative. 
Wm. H. DALL. 
U. S. NATIONAL MusEuM, 
WASHINGTON, D. C., October 12, 1897. 
SCIENTIFIC LITERATURE. 
Hallucinations and Illusions, A Study of the 
Fallacies of Perception. By EDMUND PARISH. 
London, Walter Scott; New York, Charles 
Scribner’s Sons, 1897. Pp. 390. Contem- 
porary Science Series, Vol. XX XI. 
The present volume is a rewriting, by the 
author, of his German monograph, published 
about three years ago; and this in turn grew 
out of his examination, for the Munich Psycho- 
logical Association, of the cases collected in 
Germany for the ‘International census of Wak- 
ing Hallucinations in the Sane’—a _ project 
initiated and vigorously promoted by the Eng- 
lish Society for Psychical Research. While 
there is an extensive literature on some one or 
another of the many ramifications of the general 
subject of illusions—particularly contributions 
of cases illustrative of certain special kinds or 
causes of illusion—there is a conspicuous lack 
of more comprehensive and systematic treatises 
covering the general field, both descriptively 
and with the purpose of presenting these 
various forms of fallacious perception from 
some unifying theory or principle. 
It can hardly be said that the author has 
succeeded in filling this gap, although the road 
SCIENCE. 
[N. 8. Vou. VI. No. 147. 
which he set out to survey has been covered 
with accuracy and originality. Comparison is 
at once suggested with the older volume of 
Sully on ‘Illusions,’ which, though far less 
scientifically thorough and necessarily lacking 
in the explanations and conceptions that have 
grown out of recent research, is none the less 
more comprehensive in scope and more philo- 
sophical as well as attractive in treatment. 
The general reader will still find more enlighten- 
ment as to the nature of illusions in the work of 
Sully than in that of Parish, although he can 
find no abler treatment of certain phases of this 
study than the latter work offers. To begin 
with, Dr. Parish’s definition of his topic rules 
out the consideration of that interesting group 
of normal deceptions of the senses—commonly 
known as optical illusions and the like—which 
are so significant for the study of sense-interpre- 
tation and perception. Indeed, instead of con- 
ceiving an illusion as any form of psychological 
process which happens to be erroneous he aims 
to establish a type of perception, at times 
normal and at times abnormal, as the basis of 
all hallucinations and illusions. This under- 
lying principle is found to be that of dissocia- 
tion, ‘‘a state in which, indeed, generally 
speaking, the consciousness is normal, but where 
the association-paths of a more or less compli- 
cated system of elements are wholly or partially 
blocked.’’ Hallucinations and illusions ‘‘are 
just as much sensory perceptions as the so- 
called ‘objective’ perceptions.’? The dream 
state is an extreme state of dissociation, and as 
such hallucinations and illusions become the 
stuff that dreams are made of; in insanity and 
nervous fatigue; in moments of emotional ex- 
citement as well as of rapt attention ; under the 
influence of drugs and particularly in hypnotic 
states, the conditions are favorable for that 
distortion and inhibition of the normal associa- 
tion-paths which Dr. Parish holds to be the 
starting point of fallacious perception. 
This conception has much in its favor; it 
makes it natural to find a considerable number 
of hallucinations among the sane and in the 
waking state; it certainly binds together the 
various forms of semi-abnormal and morbid 
conditions under which illusions most commonly 
occur; it is equally adaptable to the explana- 
