APRIL 19, 1912] 
easily followed. The experiment of trans- 
posing and suturing motor nerves is success- 
ful only when nerves whose central termina- 
tions are relatively close to each other are 
used for the purpose. I am inclined to regard 
the sensory readjustment as essentially a 
dynamic rather than as an anatomical change. 
This is only a simple case, and the physiol- 
ogist does not get very far in his experiments 
without encountering more serious difficulties. 
In the higher vertebrates the situation is 
further complicated by the presence of two 
motor systems—the phylogenetically old and 
the phylogenetically new, e. g., the pyramidal 
tract, as von Monakow* has pointed out on 
morphological grounds and as I have indicated 
(1909) from experimental considerations. In 
ease of injury to any part of the newer sys- 
tem, the phylogenetically older system may 
assume, in a certain degree, the functions 
previously belonging to the newer system. 
The theory of localization of function in its 
relation to the phylogenetic development of 
the nervous system enables us to give a ra- 
tional and intelligible account of many nerve 
processes, though the lack of experimental data 
leaves others unilluminated. It is but fair to 
state in this connection that the only physiol- 
ogist of modern times who maintained a per- 
fectly consistent attitude on cerebral localiza- 
tion was Goltz, who denied it in toto. 
It follows, as a consequence of the postu- 
late of integration, that the character of the 
activity of any particular mechanism is de- 
termined, not by any one constituent part, but 
that the final action is the sum of the activi- 
ties of the various constituent parts. A 
change in the relation of the afferent im- 
pulses produces a change in the motor reac- 
tion. Indeed, we may probably say that if all 
the relations are the same in two successive 
processes, even though they may be separated 
in point of time, the motor reactions must 
necessarily be alike. This is certainly true of 
some reactions, and may be regarded as a re- 
statement of Hermann’s law of specific re- 
2¢¢Anfbau und Lokalisation der Bewegungen 
beim Menschen,’’ Leipzig, 1910; ‘‘ Uber Lokalisa- 
tion der Hirnfunktionen,’’? Wiesbaden, 1910. 
SCIENCE 
621 
sponse to stimulation, and is in line with C. 
O. Whitman’s wider generalization that “ or- 
ganization shapes behavior.” 
The theory of integrative action may be ex- 
tended to the field of the special senses. The 
psychologists, or certain of them, have argued 
that, since neither the afferent nerves of 
special sense nor the central cells about which 
they terminate are sufficiently different ana- 
tomically from other afferent nerves or central 
cells to explain the specific energy of the sen- 
sory nerves, this difference in sensation must 
depend upon consciousness. In this they have 
been but miserable comforters. Since no one 
has yet told us what consciousness is, attribu- 
ting a certain function to consciousness is 
tantamount to saying that we know little 
about it. If the ultimate sensation of which 
we become aware is due not to a single affer- 
ent nerve and a circumscribed end station 
alone, but to the peculiar relationships of these 
structures to other parts of the nervous sys- 
tem as well, the aspect of the problem 
changes somewhat. The visual sensations, for 
example, may be the resultant of afferent im- 
pulses over the optic nerve acting on various 
central stations, some of which, as shown by 
the course of the association tracts, may be 
remote from the occipital area of the cerebral 
cortex. If a particular sensation is the result 
of the action of a definitely localized inte- 
grating mechanism, consciousness, in so far 
as it deals with this particular sensation, is 
also a result of the activity of a definite or- 
ganization, morphological and functional, of 
the brain, and is related to a fairly definite 
region or regions. It is doubtful whether the 
psychologists are in possession of sufticient 
facts to show that such a hypothesis of inte- 
gration is impossible or even improbable. 
Few physiologists will deny that our analysis 
of the motor system and, a fortiori, of the 
system of the special senses, is incomplete, 
and that we do not yet know all we need to 
Inow about them. Few will deny that the 
analysis is difficult, and that we may be a long 
time finding out. I am free to admit the 
possibility that the views stated here may not 
be the final views in the matter. I am ex- 
