24 THE STOKY OF LIFE'S MECHANISM. 



composition, and that the more complex the 

 compound the more varied its properties. It 

 was a natural conception, therefore, that proto- 

 plasm 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 com- 

 position. It followed from this conclusion that 

 if chemists ever succeeded in manufacturing the 

 chemical compound, protoplasm, 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 

 is evident that the aim of biological study must 

 be to test these conceptions and carry them out 

 into .details. The chemical and mechanical laws 

 of nature must be applied to vital phenomena in 

 order to see whether they can furnish a satisfac- 

 tory explanation of life. Are the laws and forces 

 of chemistry sufficient to explain digestion ? Are 

 the laws of electricity applicable to an under- 

 standing of nervous phenomena ? Are physical 

 and chemical forces together sufficient to explain 

 life ? Can the animal body be properly regarded 

 as a machine controlled by mechanical laws ? Or, 

 on the other hand, are there some phases of life 



