THE STORY OF NINETEENTH-CENTURY SCIENCE 



appreciation of the great law of conservation. Blood- 

 letting, the modern physician holds, was a practice of 

 very doubtful benefit, as a rule, to the subject ; but once, 

 at least, it led to marvellous results. No straw is so small 

 that it may not point the receptive mind of genius to 

 new and wonderful truths. 



Here, then, was this obscure German physician, lead- 

 ing the humdrum life of a village practitioner, yet seeing 

 such visions as no human being in the world had ever 

 seen before. 



The great principle he had discovered became the 

 dominating thought of his life, and filled all his leisure 

 hours. He applied it far and wide, amidst all the phe- 

 nomena of the inorganic and organic worlds. It taught 

 him that both vegetables and animals are machines, 

 bound by the same laws that hold sway over inorgan- 

 ic matter, transforming energy, but creating nothing. 

 Then his mind reached out into space and met a universe 

 made up of questions. Each star that blinked down at 

 him as he rode in answer to a night call seemed an inter- 

 rogation-point asking, How do I exist? Why have I 

 not long since burned out if your theory of conservation 

 be true ? No one hitherto had even tried to answer that 

 question; few had so much as realized that it demanded 

 an answer. But the Heilbronn physician understood 

 the question and found an answer. His meteoric hy- 

 pothesis, published in 1848, gave for the first time a 

 tenable explanation of the persistent light and heat of 

 our sun and the myriad other suns an explanation to 

 which we shall recur in another connection. 



All this time our isolated philosopher, his brain aflame 

 with the glow of creative thought, was quite unaware 

 that any one else in the world was working along the 



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