1885.] The Relations of Mind and Matter. 757 
compared with electricity, and that the peculiar conditions of the 
instigating influence persist in the current. Yet though the nerve 
current moves slowly there is no indication that it meets any 
check in the conducting fiber or in the organ of sense reception. 
Probably every motor influence that can make its way through 
the outer surface to the nerve endings, of sufficient vigor to in- 
duce chemical action in or otherwise affect these endings, pro- 
duces a nerve current without reference to its character. And 
every such current received by the nerves is transmitted and appa- 
rently even strengthened as it flows inward. 
How is it, then, that some such currents pass directly onward 
to the muscles, while others are checked and disappear as cur- 
rent influences? There is strong indication that the ganglia per- 
form this duty. The diminution of the diameter of the fiber in 
the nerve cell is a precise equivalent of the method adopted to 
produce the same effect upon the electric current. But the point 
here to consider is that of the evident discrimination displayed. 
In the sympathetic nerve system there is no evidence of such dis- 
crimination. There is a checking influence exerted, but it acts 
upon all currents alike. Each fiber probably passes through a 
chain of ganglia, each of which lowers the intensity of the cur- 
rent until itis finally unable to force its way further. Thus the 
distance to which a sympathetic current will flow depends upon 
its original strength. When, for instance, in the process of diges- 
tion the sympathetic nerve extremities are excited by the-contact 
of food, certain muscles are affected, and produce the peristaltic 
movement of the intestine. If the contact influence is slight, this 
movement will be slight and local. If contact be vigorous the 
effect will grow more energetic and extend further, while a wider 
range of glands will be excited to action. If the contact influ- 
ence be abnormaily vigorous the effect will pass onward from the 
sympathetic to the spinal nerves, and the cerebrum be notified of 
the abnormal condition, while its motor lines of connection with 
the sympathetic nerves will be called into activity. We have 
every reason to believe that it is the ganglion not the fiber that 
thus diminishes the energy of the current. And the distance to 
which this current can travel depends on its vigor and the num- 
ber of ganglia through which it is able to force its way. ` 
The same is the case with the cerebro-spiral nerve system. 
Nerve impulses of a character that ıs usually checked may force 
