190 ZOOLOGICAL PHILOSOPHY 



animals there is a high complexity and great intricacy in the combina- 

 tion of principles. Living bodies thus constitute, by their possession 

 of life, nature's principal means for bringing into existence a number 

 of different compounds which would never otherwise have arisen. 



It is vain to imagine that living bodies find ready formed in the 

 substances on which they feed all the material required for building 

 up the various parts of their bodies ; they only find in these food 

 substances, materials suitable for entering into the combinations 

 which I have mentioned, and not the combinations themselves. 



It is no doubt owing to an insufficient study of the power of life in 

 the bodies which possess it, and the failure to perceive the results 

 of this power, that it has been alleged that living bodies find in their 

 ordinary food the material ready prepared which serves for building 

 up their bodies and that these materials have existed in nature for all 

 time. 



Such are the subjects which compose the second part of this work : 

 their importance would no doubt justify considerable expansion ; 

 but I have confined myself to a concise exposition of what is necessary 

 in order that my observations may be understood. 



