148 THE POPULAR SCIENCE MONTHLY 



1783 he and Laplace reported the results of their investigations on the 

 subject of life to the Paris Academy of Sciences, but had little to say 

 about the nature of life itself. In 1839 the British Association re- 

 quested Liebig to study the subject of biology, as it then existed, and 

 report at a subsequent meeting all that was known about it. The 

 report was thorough, valuable and gave great satisfaction, but shed no 

 light on the origin and nature of life. Though a vitalist, Liebig gave 

 less attention to the defence of this belief than to the applications of 

 the principles of chemistry to economics, especially as related to agri- 

 culture. Here his efforts were epoch-making. John Miiller, of Berlin, 

 and the Weber brothers, of Leipzig, investigated the physical and me- 

 chanical processes of life, so far as they could trace them by careful ex- 

 periment in the laboratory. Du Bois Beymond and Helmholtz were 

 trained by Miiller and were among his most distinguished pupils. 



It was while seeking answers to questions which investigations as to 

 the origin and nature of life were constantly presenting that Helmholtz 

 and Meyer, in entire independence of each other, discovered the prin- 

 ciple of the conservation of force or energy. In 1847 Helmholtz proved, 

 as he thought beyond any reasonable doubt, that living forces are 

 manifestations of a certain quantity of power to do work. The out- 

 come of these studies and the publication of theories based upon them 

 brought about a change, in Germany especially, in the opinions hitherto 

 held as to the nature of the vital force or vital principle. Not a few 

 were content to reduce life to a mechanical process and to deny any 

 distinction between life and matter. Others sought to discover the life 

 process and to make its development clearer by many different theories. 

 The " potential energy " of Helmholtz, the cell formation theory of 

 Schwann, set forth in 1839, and the theory of Max Verworn, of Jena, 

 that life consists in the " metabolism of proteids " do not require the 

 supposition of any principle or force apart from matter itself to 

 account for life in any of the forms in which it has appeared. And yet 

 these theories do not deny the possibility of the existence of a life 

 principle. Neither does acceptance of the " physiological unit," as sug- 

 gested by Mr. Herbert Spencer, prevent us from believing that life may 

 be something quite different from this unit and independent of it even 

 if it manifest itself in and through it. Accurately as these life processes, 

 as they are termed, have been traced by the most capable experimenters 

 in the world, the product of these experiments, however exactly it 

 imitate that of nature differs from it in toto. The laboratory product 

 may contain the same elements, and so far as can be seen, arranged in 

 the same proportion, and yet be entirely unlike the product of nature. 

 No chemist has yet learned how to arrange atoms of matter in a living 

 organism and adapt that organism to an environment in any such way 

 as to compete with nature or indeed to give to the product of the 

 laboratory anything worthy of being called life. 



