31 G THE CAUSES OF THE xi 



our bodies are composed are largely, in all 

 probability, the substances which constituted the 

 matter of long extinct creations, but which have 

 in the interval 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 ? 

 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 



