316 THE CAUSES OF. THE XT 
our bodies are composed are largely, in all 
probability, the substances which constituted the 
matter of long extinct creations, but which have 
in the anterval constituted a part of the inorganic 
world. 
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 philo- 
sophers 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 ? 2 
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, inte: 
