2O THE LIVING WORLD. 



was for a long time believed that they could never 

 be obtained except through the influence of vitality. 

 Modern chemistry has demonstrated the possibility 

 of making many of them in the laboratory ; many of 

 the simpler ones have already been manufactured, 

 and the list is constantly increasing. 



Plainly, however, the destructive processes are by 

 no means so important as the constructive ones. In 

 plants the simplest compounds, H 2 O, CO 2 , and 

 NH 3 are built under the influence of sunlight, into 

 the most complicated ones. Even in animals this 

 constructive power is essential, for they do not con- 

 tent themselves with simply pulling to pieces the 

 products of the life of plants. They do destroy most 

 of them, but the energy liberated enables them to do 

 a certain amount of building for themselves. They 

 change dead matter into living matter, which must 

 be looked upon as a constructive process. Now our 

 chemists tell us that they have reason for believing 

 that even these constructive processes are purely 

 chemical, and will one day be simulated in the lab- 

 oratory. They have, indeed, already shown that 

 many of these organic bodies can be manufactured 

 synthetically. Plants manufacture protoplasm, the 

 most complicated body of which we have any 

 knowledge. By the decomposition of this body may 

 be obtained a long series of decomposition products, 

 which become simpler and simpler until they are 

 once more resolved into the simple ones with which 

 the plant started. Now our chemists have begun 

 with these simple bodies, CO 2 , H 2 O, NH 3 , etc., 

 and have begun to climb this ladder of compounds 



