THE WONDERS OF LIFE 



these circumstances, it seems advisable, at the com- 

 mencement of our philosophic study of "the wonders 

 of life," to form a clear idea of our task. We must 

 carefully define the place of biology among the sciences, 

 and the relation of its various branches to each other 

 and to the different systems of philosophy. 



In the broadest sense in which we can take it, biology 

 is the whole study of organisms or living beings. Hence 

 not only botany (the science of plants) and zoology 

 (the science of animals), but also anthropology (the 

 science of man), fall within its domain. We then 

 contrast with it all the sciences which deal with in- 

 organic ot- lifeless bodies, which we tndy collectively call 

 abiology (or anorganology) ; to this belong astronomy, 

 geology, mineralogy, hydrology, etc. This division of 

 the two great branches of science does not seem difficult 

 in view of the fact that the idea of life is sharply dfefined 

 physiologically by its metabolism and chemically by its 

 plasm; but when we come to stildy the questibn of 

 abiogenesis (chaptet xv.) we shall fimd that this division is 

 not absolute, and that organic life has been evolved from 

 inorganic nature. Moreover, biology and dbiology are 

 connected branches of cosmology, or the science of the 

 world. 



While the idea of biology is now usually taken in this 

 broad sense in most scientific works and made to embrace 

 the whole of living nature, we often find (especially in 

 Getmany) a narrower application of the term. Many 

 authors (mostly physiologists) understand by it a 

 section of physiology — namely, the science of the rela- 

 tions of living organisms to the external world, their 

 habitat, customs, enemies, parasites, etc. I ptoposed 

 long ago to call this special part of biology oecology (the 

 science of hottie-relations), or bionomy. Twenty j^ears 

 later others suggested the name of ethology. To call 

 this special study any longer biology in the narrower 



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