THE CELL AND PROTOPLASM. 8 1 



mechanics, we have here in this mechanical theory 

 of life the complete reduction of the body to a 

 machine. 



The Reign of Protoplasm. This substance pro- 

 toplasm became now naturally the centre of bio- 

 logical thought. The theory of protoplasm arose 

 at about the same time that the doctrine of 

 evolution began to be seriously discussed under 

 the stimulus of Darwin, and naturally these two 

 great conceptions developed side by side. Evolu- 

 tion was constantly teaching that natural forces 

 are sufficient to account for many of the com- 

 plex phenomena which had hitherto been regard- 

 ed as insolvable ; and what more natural than the 

 same kind of thinking should be applied to the 

 vital activities manifested by this substance proto- 

 plasm. While the study of plants and animals 

 was showing scientists that natural forces would 

 explain the origin of more complex types from 

 simpler ones through the law of natural selection, 

 here in this conception of protoplasm was a theory 

 which promised to show how the -simplest forms 

 may have been derived from the non-living. For 

 an explanation of the origin of life by natural 

 means appeared now to be a simple matter. 



It required now no violent stretch of the im- 

 agination to explain the origin of life something 

 as follows : We know that the chemical elements 

 have certain affinities for each other, and will 

 unite with each other under proper conditions. 

 We know that the methods of union and the re- 

 sulting compounds vary with the conditions under 

 which the union takes place. We know further 

 that the elements carbon, hydrogen, oxygen, and 

 nitrogen have most remarkable properties, and 

 unite to form an almost endless series of remark- 



