516 THE THEORY OF ENERGY AND THE LIVING WORLD. 



in such a light as to lend them the importance they deserved. From 

 that moment the name of the modest physician of Heilbronn has taken 

 rank among - the most illustrious scientists. 



As to the science of energetics, of which thermodynamics is but a 

 single section, it must be admitted that even if it does not already 

 absorb mechanics, astronomy, physics, chemistry, and physiology, and 

 constitute the general and, for the future, unique natural science, still 

 it constitutes a preliminary movement toward that ideal state and a 

 long step in the pathway of progress. 



We propose to illustrate these new ideas, first in their general bear- 

 ing and then with special reference to their application to physiology, 

 or, in other words, their influence on the phenomena of life. 



According to most physicists the phenomena of the universe call 

 into play two, and only two, elementary and fundamental things, to 

 wit, matter and energy. All that we see consists in changes in the 

 one or the other of these two forms. This is, one might say, the postu- 

 late of experimental science. 



To be sure, it is difficult to give a definition to the conception of 

 matter satisfactory to the metaphysicists. It will always be admissible 

 to discuss or even to deny its existence. Even the physicist or physi- 

 ologist, convinced that man knows nothing except through his own 

 sensations, and that he makes nothing of them except he first objectiv- 

 ize or project them from himself by some sort of hereditary illusion, 

 may hesitate in ascribing an objective character to matter. Another 

 difficulty presents itself even after this one is gotten over and matter 

 comes to be defined as that which has extension or weight or mass. 

 For, as regards weight as the characteristic of matter, physicists 

 recognize a certain imponderable kind of matter, the ether, which has 

 only a sort of logical existence, founded on the necessity of a medium 

 for the propagation of heat, light, and electricity. As regards mass — 

 that is, the mechanical parameter — it is necessary to introduce the term 

 energy, or the allied term, force, in order to define mass, so that we 

 should consequently be defining matter in terms of energy. Thus there 

 appears to be some reason to think the two fundamental elements not 

 irreducible. 



It is necessary to avoid these difficulties. The physicist neglects 

 them provisionally; that is to say, he defers their consideration. As a 

 first approximation matter may be considered as that which has 

 weight. Through chemistry we learn that matter has many forms. 

 There are simple substances, classed as metals and metalloids, aud 

 compounds, either organic or inorganic. Chemistry may be called the 

 history of the mutations of matter. From the time of Lavoisier its 

 transformations have been followed, balance in hand, and it has been 

 shown that they all take place without change of weight. If we 



