ee eT 
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1885. ] The Relations of Mind and Matter. 1065 
differ from those on canvas in the perfection of their perspective 
and of their arrangement of light and shade, The effect on the 
mind may be that which any picture that was absolutely perfect 
in these respects would produce on the eye. 
If we continue to view the mind as a substantial organism, and 
its conditions as due to the motor relations of the parts of this 
organism, the mode of impression of a formal image on it may 
bear some relation to photography. 
It may seem inexplicable that the same nerve fiber in convey- 
ing currents of energy can yield such different impressions as 
these currents vary in their source. It might be argued that such 
currents could only differ in degree and not in kind. And yet 
the eye receives its pictures from currents of energy conveyed 
through a single medium, that of the vibrating ether. The varia- 
tions in light and shade, color, &c., are due to variations in the 
conditions of this energy, and similar variations may exist in the 
nerve current. As an object photographs itself, through the 
effects of these variations in the energy of light, on a sensitive 
tablet, so the retinal picture of such an object, through similar 
variations in the energy of the nerve current, may produce an 
analogous effect on the sensitive mental tablet. 
The idea of photography, of course, is offered but as an illus- 
tration of a sensitiveness of inorganic substance which imitates, 
though remotely, that of the mind. In the instantaneous pho- 
tography of recent years plates are made of such exquisite sen- 
Sitiveness as to take a good picture in a very minute fraction 
of a second. While these plates are kept from the light no 
change is produced in them. The instant the light falls upon 
them an exact surface copy of the object from which it emanates 
is produced on the sensitive plate. And this picture becomes a 
permanent condition of the plate. Some change has been pro- 
duced in its motor or chemical organization, and the picture 
remains an indissoluble characteristic of its subsequent organiza- 
tion! The parallel this presents to the mind, viewed as a sensi- 
1In illustration of the sensitiveness of material surfaces we may quote from Pro- 
of the wafer comes into view, and this may be done again and again. Nay, — 
more, if the polished metal be carefully put aside, and be so kept for many months 
