Marcu 1, 1912] 
It is the principle of localization which 
must be debated and settled. Whether it 
is the mental processes or cells which are 
localized is a matter which apparently the 
histologists and clinicians have not settled. 
It may be admitted that cells and eell 
groups are localized, and, although there is 
some doubt on the part of some clinicians, 
we may be willing to admit that certain 
symptoms are produced by definite lesions. 
We have, however, no evidence which will 
warrant the conclusion that mental states 
have been localized, and it is doubtful that 
many psychologists will believe in the 
erude histological localization of mental 
processes. The histological, the physiolog- 
ical and the clinical evidence warrants 
only a belief in the possibility of an asso- 
ciation of brain lesions with motor, sensory 
and associational derangements, it does not 
warrant a belief in psychic localization. 
Although it is apparent that mental 
states are not to be found spatially asso- 
ciated with definite areas distinguished 
from one another by histological and mac- 
roscopical characteristics, for practical 
purposes we must admit a close connection 
between the brain and mental processes. 
How then shall we conceive of the relation 
between the activities of the brain and 
mental states? The functions of the ner- 
vous cells, as functions, may include some- 
thing which is at the basis of psychological 
states, but at the present time the physical 
and chemical activities of the cells can not 
be believed to be equivalents of the mental 
processes which may be concomitant with 
or the result of these activities. Since for 
practical purposes we may need some gen- 
eral principle of localization, we may say 
that mental processes are not due to the 
independent activities of individual parts 
of the brain, but to the activities of the 
brain as a whole. Here also I would not 
omit the cerebellum. It is well known that 
SCIENCE 
327 
similar mental processes may be inhibited 
by or may be lacking because of lesions in 
parts of the brain widely separated. This 
fact is the one at the basis of the diaschesis 
hypothesis of von Monakow. This hy- 
pothesis explains only certain clinical man- 
ifestations; it explains certain losses and 
how the same symptoms may be produced 
by diverse lesions. Conversely, it helps 
towards a proper understanding of the 
brain processes in connection with mental 
states. The individual parts of the brain 
do not work independently; they work in- 
terdependently, and it is because of the 
possible functional and anatomical connec- 
tions that certain types or kinds of mental 
states are more in evidence than others. 
We should, on the physiological side, be 
not far wrong, if we compared the brain 
to a village or city as did Gregoire of Nice. 
There are paths and streets, definitely re- 
lated to one another, but each independent 
to a certain extent. There are broad roads 
with many travelers, there are paths only 
occasionally traversed. There are houses 
from which the people come and to which 
they go; some pouring forth people in 
streams, others only occasionally; to some 
numerous people go and to others few. 
What goes on in the houses we can not tell. 
We can observe the ‘‘from’’ and the 
‘‘where,’’ the structure of the houses, and 
numerous other anatomical and histological 
facts, the effects of blocking of paths and 
streets and the destruction of houses, but 
the purposes of the travelers we do not 
know. We may have for the city a his- 
tological and a clinical localization, but 
this does not mean that we have also a 
mental localization. 
From the anatomical and physiological 
standpoint, we deal solely with associations 
of an anatomical and physiological char- 
acter. With these physiological assecia- 
tions mental processes are supposed to be 
