384 
POPULAR SCIENCE REVIEW. 
which produced in over quantity oppresses us ; which produced 
in too small quantity is insufficient for our wants ; which is 
renewed by food and by sleep, exhausted by wakefulness and 
labour ; which receives every vibration or motion from without, 
and lets the same vibrate into us, to be fixed or reflected back ; 
and which conveys the impulse when we will an act and per- 
form it. 
It may be urged that in this line of thought is included no 
more than the theory of the existence of the ether that is sup- 
posed to pervade space, the undulating ether of light. It 
may be said that this universal ether pervades all the organism 
of the animal body as from without, and as part of every 
organisation. This view would be Pantheism physically dis- 
covered, if it were true. It fails to be true because it would 
destroy the individuality of every individual being : it fails to 
be true because it would destroy the individuality of every in- 
dividual sense. If we did not individually produce, by our own 
chemistry, the refined essence pervading us ; if the essence were 
diffused through us independently of our eating, drinking, 
breathing, we should be independent of the earth altogether, 
endowed with an indestructible physical existence not belonging 
to us at all, specially, but to the universe at large, and distinct 
from us ; we should, in fact, be as atoms of matter aggregated 
by attraction into a certain form or mould, and held to the 
earth by the attraction of the earth, but actually permeated 
with the ether, as though we floated in an ethereal sea. If we 
did not individually produce the medium of communication 
between ourselves and the outer world, if it were produced 
from without and adapted to one kind of vibration alone, then 
were fewer senses required than we possess ; for, taking two 
illustrations only — ether of light is not adapted for sound, 
and yet we hear as well as see ; while air, the medium of motion 
of sound, is not the medium of light, and yet we see and hear. 
In the theory therefore I offer the nervous ether is an 
animal product. In different classes of animals it may differ 
in physical quality so as to be adapted to the special wants of 
the animal, but essentially it plays one part in all animals, and 
is produced, in all, in the same way. 
I think I may venture, to some extent, to define the required 
physical properties of a nervous ether. We may consider it as 
a gas or vapour, and as having in its elementary construction 
carbon, hydrogen, and possibly nitrogen : I suspect it is con- 
densable under cold, movable under pressure, diffusible by 
heat, insoluble in the blood, and holding at the natural tem- 
perature of the body a tension requisite for natural function. 
It is retained, I imagine, for a longer time in cold-blooded 
animals, after death, than in warm-blooded animals, and 
