682 The Relations of Mind and Matter. [July 
mass motion. But in all the higher animals other effects are pro- 
duced. All the nerve fibers enter cells or masses of cells called 
ganglia, though there is no evidence that they end there. There 
is some reason to believe that they simply pass through these 
cells, with a reduction of diameter, and perhaps a division into 
branches. All we can be sure of is that the motor energy which 
they carry inward does not all pass through these ganglia, but 
that much of it is arrested in its course and there distributed. 
And in this distribution an interesting feature of the case is, at 
least so far as the cerebral ganglion is concerned, that the motor 
energy retains the peculiarities it possessed before entering the 
body, or something equivalent to them, and impresses a perma- 
nent record of each such peculiarity upon some internal tablet. 
Only when this energy continues its course over the nerves to the 
muscles does it lose its individuality and merge in the general 
outflow of muscle energy. 
As we descend in the animal kingdom it is to find this com- 
plex apparatus of sensation and motion gradually simplify. The 
sensory nerve-endings and their organs grow less intricate, and 
their susceptibility is diminished. Some of the organs of special 
sense completely disappear, and the power of the others becomes 
little more than a modified touch. In very many cases the body 
is covered by a rigid armor, and the influence of external energy 
is limited to a small region of the surface. Finally the special 
senses disappear, apparently the last to vanish being that of sight, 
which is reduced to a vague discrimination between light an 
shade. _The cerebral ganglion grows less and less marked, and 
disappears as a special organ. Finally the nerve and muscle 
fibers vanish, one of their last traces being the single cell which, 
in the Hydra, appears to function both as nerve and muscle. On 
reaching the Protozoa we find forms quite destitute of sensory 
and motor organs, And yet sensation and motion persist. These 
_ powers seem to be native to protoplasmic matter, however aggre- 
gated, and are displayed even in the plant cell wherever it is so 
situated that its protoplasm is exposed to external energy. 
Yet late discoveries in regard to the constitution ofthe cell 
_ prove it to be by no means the simple homogeneous structure 
: nd supposed, The division into nucleus and outer cell 
has bi traced to a very low level, and perhaps exists at the low- 
- Anad the nucleus, and to a less marked extent the outer 
a 
