14 THE STORY OF THE LIVING MACHINE. 



This mechanical conception of living activity 

 was carried even farther. Under the lead of Hux- 

 ley there arose in the seventh decade of the cen- 

 tury a view of life which reduced it to a pure 

 mechanism. The microscope had, at that time, 

 just disclosed the universal presence in living 

 things of that wonderful substance, protoplasm. 

 This material appeared to be a homogeneous sub- 

 stance, and a chemical study showed it to be made 

 of chemical elements united in such a way as to 

 show close relation to albumens. It appeared to 

 be somewhat more complex than ordinary albu- 

 men, but it was looked upon as a definite chemical 

 compound, or, perhaps, as a simple mixture of 

 compounds. Chemists had shown that the proper- 

 ties of compounds vary with their composition, 

 and that the more complex the compound the 

 more varied its properties. It was a natural con- 

 ception, therefore, that-protoplasm was a complex 

 chemical compound, and that its vital properties 

 were simply the chemical properties resulting 

 from its composition. Just as water possesses the 

 power of becoming solid at certain temperatures, 

 so protoplasm possesses the power of assimilating 

 food and growing ; and, since we do not doubt 

 that the properties of water are the result of its 

 chemical composition, so we may also assume that 

 the vital properties of protoplasm are the result 

 of its chemical composition. It followed from 

 this conclusion that if chemists ever succeeded in 

 manufacturing the chemical compound, proto- 

 plasm, it would be alive. Vital phenomena were 

 thus reduced to chemical and mechanical problems. 



These ideas arose shortly after the middle of 

 the century, and have dominated the development 

 of biological science up to the present time. It 



