THE CELL AND PROTOPLASM. 97 



compound was a very unstable compound, just 

 as is a mass of gunpowder, and hence it is highly 

 irritable, also like gunpowder, and any disturb- 

 ance of its condition produces motion, just as a 

 spark will do in a mass of gunpowder. It is 

 capable of inducing oxidation in foods, some- 

 thing as water induces oxidation in a bit of 

 iron. The oxidation is, however, of a different 

 kind, and results in the formation of different 

 chemical combinations ; but it is the basis of 

 assimilation. Since now assimilation is the 

 foundation of growth and reproduction, this 

 mechanical theory of life thus succeeded in trac- 

 ing to the simple properties of the chemical com- 

 pound protoplasm, all the fundamental properties 

 of life. Since further, as we have seen in our first 

 chapter, the more complex properties of higher or- 

 ganisms are easily deduced from these simple ones 

 by the application of the laws of 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 protoplasm became now natur- 

 ally the centre of biological 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. Evolution was constantly teaching 

 that natural forces are sufficient to account for 

 many of the complex phenomena which had 

 hitherto been regarded as insolvable ; and what 

 more natural than that the same kind-of thinking 

 o 



