THE BELFAST ADDRESS. 181 



itself everywhere in nature. Long in advance of all 

 definite experiment upon the subject, the constancy and 

 indestructibility of matter had been affirmed ; and all 

 subsequent experience justified the affirmation. Mayer 

 extended the attribute of indestructibility to energy, 

 applying it in the first instance to inorganic, 1 and after- 

 wards with profound insight to organic nature. The 

 vegetable world, though drawing all its nutriment 

 from invisible sources, was proved incompetent to gene- 

 rate anew either matter or force. Its matter is for the 

 most part transmuted gas ; its force transformed solar 

 force. The animal world was proved to be equally un- 

 creative, all its motive energies being referred to the 

 combustion of its food. The activity of each animal, 

 as a whole, was proved to be the transferred activity of 

 its molecules. The muscles were shown to be stores of 

 mechanical energy, potential until unlocked by the 

 nerves, and then resulting in muscular contractions. 

 The speed at which messages fly to and fro along the 

 nerves was determined by Helmholtz, and found to be, 

 not, as had been previously supposed, equal to that of 

 light or electricity, but less than the speed of sound 

 less even than that of an eagle. 



This was the work of the physicist : then came the 

 conquests of the comparative anatomist and physiolo- 

 gist, revealing the structure of every animal, and the 

 function of every organ in the whole biological series, 

 from the lowest zoophyte up to man. The nervous sys- 

 tem had been made the object of profound and con- 

 tinued study, the wonderful and, at bottom, entirely 

 mysterious controlling power which it exercises over the 

 whole organism, physical and mental, being recognised 

 more and more. Thought could not be kept back from 



1 Dr. Berthold has shown that Leibnitz had sound views re- 

 garding the conservation of energy in inorganic nature. 



