Thus we come to the conclusion, strange at first sight, that the MATTER
constituting the living world is identical with that which forms the
inorganic world. And not less true is it that, remarkable as are the
powers or, in other words, as are the FORCES which are exerted by
living beings, yet all these forces are either identical with those
which exist in the inorganic world, or they are convertible into them;
I mean in just the same sense as the researches of physical
philosophers have shown that heat is convertible into electricity, that
electricity is convertible into magnetism, magnetism into mechanical
force or chemical force, and any one of them with the other, each being
measurable in terms of the other,--even so, I say, that great law is
applicable to the living world. Consider why is the skeleton of this
horse capable of supporting the masses of flesh and the various organs
forming the living body, unless it is because of the action of the same
forces of cohesion which combines together the particles of matter
composing this piece of chalk? What is there in the muscular
contractile power of the animal but the force which is expressible, and
which is in a certain sense convertible, into the force of gravity
which it overcomes? Or, if you go to more hidden processes, in what
does the process of digestion differ from those processes which are
carried on in the laboratory of the chemist? Even if we take the most
recondite and most complex operations of animal life--those of the
nervous system, these of late years have been shown to be--I do not say
identical in any sense with the electrical processes--but this has been
shown, that they are in some way or other associated with them; that is
to say, that every amount of nervous action is accompanied by a certain
amount of electrical disturbance in the particles of the nerves in
which that nervous action is carried on. In this way the nervous action
is related to electricity in the same way that heat is related to