758 The Relations of Mind and Matter. [August, 
their way inward if exceptionally vigorous, and act upon the mus- 
cles. And significantly, in such cases, the motion produced is 
not special and definite but vague and general. The impulse, 
when it has forced a passage through the ganglia, does not select 
one motor channel in preference to others, but makes its way 
over the most conductive portion of the general motor system 
and calls many widely separated muscles into action. In this we 
have an indication of the original action of the nervous system, 
such as existed before specialization began and such as yet seems 
to exist in the sympathetic system. 
The action of the ganglia, then, appears to be at once repres- 
sive and discriminative. Certain motor influences seem more 
capable of forcing a passage through the ganglionic resistance 
than others. The principle here involved seems to be that every- 
motor influence of a new or unusual character is resisted, and 
ready passage is only allowed to motor influences to which the 
fibrilla have become adapted. And here natural selection has 
come actively into play. Let us suppose the animals of a cer- 
tain species to be subject to a definite series of motor impressions, 
each of which makes it way through the gangliar obstruction 
and tends to flow out generally to the muscular organs. Yet 
being insufficient in quantity to occupy every nerve, it will follow 
the largest, or those over which it finds the most open channel. 
Thus while the responsive movement might be somewhat gen- 
eral, certain muscles would obtain a surplus of the current and 
respond more vigorously than the others. In such a case natu- 
ral selection must rapidly operate. The movements of some 
individuals would prove protective. Others would perish. And 
on the principle that the current of energy finds easiest way over 
the channel which it has already traversed, this particular motor 
influence would pursue its old channel in preference and 
resisted by the other nerves. In like manner others of the sen- 
sory impressions might gain other favorite channels, and every 
Sensation in time produce a particular action, adapted to the high- 
est good of the animal. 
But if the nerve fibers are only readily conductive to familiar 
motor influences, and if the gangliar cells resist all unusual sen- 
= Sory Currents, another element comes into the situation. It is 
‘Rot only a question of the selection by the sensory currents of 
= certain motor nerves in preference to others, but also of making 
