620 
loses nothing in definiteness of location or of 
function. The conception of a circumscribed 
motor center must be superseded by the con- 
ception of a motor system or mechanism. It 
is to such a mechanism that we may apply 
the conception of integration as developed by 
Sherrington. Integration is essentially a 
dynamic rather than a morphological process; 
but integration implies a certain definiteness 
of relationships, morphological as well as 
dynamic, throughout any one process. We 
have already stated that stimulation of the 
particular group of cells always evokes a re- 
sponse of a particular group of muscles—con- 
traction of one set and relaxation of their 
antagonists. And since this phenomenon of 
group movement is constant from day to day 
or year to year in any one individual, we are 
justified in assuming that a certain rather 
constant morphological mechanism integrates 
certain rather constant relations in time and 
space to a fairly constant result. This is the 
essence of the modern dynamic view of lo- 
ealization of function. 
Let us apply this conception to the solution 
of one of the problems which puzzle Professor 
Franz. He cites the experiments of dividing 
two motor nerves and suturing the central end 
of one to the peripheral end of the other, with 
the subsequent recovery, after a period of 
paralysis, of movement in the respective 
groups of muscles supplied. The regeneration 
of the nerves undoubtedly means that muscle 
group A is now innervated by fibers arising 
from cells in the area which previously sup- 
plied muscle group B. There is no necessity 
for postulating any further anatomical change, 
and no basis in fact for such a postulate, even 
if it were necessary, since no new nerve cells 
arise after birth in the forms used for the ex- 
periment. We must seek an explanation, 
either in the relationships of the cells and 
their life processes, or in the entrance of some 
psychic or mental factor (and hence on Pro- 
fessor Franz’s own argument, some unknown 
factor so far as its localization is concerned) 
into the readjustment. 
Fortunately, the relationships of the cells 
and their life processes offer us some hope of 
SCIENCE 
[N.S. Vou. XXXV. No. 903 
a solution. We have already mentioned the 
fact that the cellular insula is in relation with 
practically every other portion of the same 
cerebral hemisphere, and we should empha- 
size the fact that the response of the motor 
cells is determined largely by these afferent 
impulses. In the absence of afferent impulses 
from the muscles to which they send fibers, the 
motor cells cause an uncertain and inaccurate 
response. The mechanism of integration, 
while not completely wrecked, is damaged and 
rendered inaccurate. In the process of re- 
generation of the severed nerves, the sensory 
(in case it was previously interrupted) as 
well as the motor connection of the muscle 
with the cortex has been restored. Impulses 
coming in over the old sensory route and 
reaching their usual motor cell destination in 
the cortex will now produce confusion of 
motor response. But the ocular path is open 
and the animal sees its limbs. An animal 
which has lost all sensation in a limb, through 
section of the sensory roots, becomes able to 
control the movements of the apzsthetie limb 
through its visual mechanism. When the 
eyes are bandaged, the motor embarrassment 
of the apesthetic limb returns. (Bickel.) 
The ocular path affords one possible, and 
probable, explanation of the return of motor 
function in the muscle groups whose nerves 
were severed. But the possibilities of recov- 
ery after transposing and suturing the nerves 
are by no means exhausted. The afferent im- 
pulses from the muscles do not reach their 
motor cell destinations over one neurone, but 
over a series of neurones. Between the cor- 
tical termination of the afferent path and the 
motor cells, there are intercalated association 
neurones. In the early period of recovery the 
confusion caused by the access of afferent im- 
pulses to the wrong motor end station pro- 
duces an unusual stress in that particular re- 
gion, and impulses may flow over previously 
unused channels, thereby eventually reaching, 
more or less indirectly, the proper destination. 
The final condition of equilibrium in the 
system will be reached when the association 
path from afferent cortical ending to the 
proper motor cell comes to be the one most 
