INTRODUCTION 



animals will be considered in order to show how the 

 functions are affected by structural development. De- 

 scriptive details which have already been presented 

 many times fully and delightfully will be reiterated 

 only in so far as may be necessary to emphasize the 

 fact that the life processes in living organisms continue 

 in direct response to an involuntary conformity to 

 natural laws. 



Each science has its own body of well-established 

 laws, yet year by year the limits of the sciences become 

 more and more vague, and their laws more and more 

 interdependent, until it is almost impossible to say 

 where one science begins and another ends. In time to 

 come, as more and more light is vouchsafed, we may 

 find that all natural phenomena are governed by a 

 single ultimate comprehensive law, of which the actions 

 of the human body and mind are but a very high 

 expression. The gaps left unexplained by the law of 

 evolution will be bridged and it will then no longer 

 be a mystery how matter first originated, became en- 

 dowed with life, and reached up to intelligence and to 

 conscience. Human thought has not yet conquered 

 these four problems, but the gradual advance and mar- 

 velous unity in the processes that we understand teach 

 us that a leap in the scheme of nature is incredible. 



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