PEEFACE. 



THAT the living body is a machine is a statement 

 that is frequently made without any very accu- 

 rate idea as to what it means. On the one hand 

 it is made with a belief that a strict comparison 

 can be made between the body and an ordinary, 

 artificial machine, and that living beings are 

 thus reduced to simple mechanisms; on the 

 other hand it is made loosely, without any 

 special thought as to its significance, and cer- 

 tainly with no conception that it reduces life to 

 a mechanism. The conclusion that the living 

 body is a machine, involving as it does a mechan- 

 ical conception of life, is one of most extreme 

 philosophical importance, and no one interested 

 in the philosophical conception of nature can fail 

 to have an interest in this problem of the strict 

 accuracy of the statement that the body is a 

 machine. Doubtless the complete story of the 

 " living machine " can not yet be told ; but the 

 studies of the last fifty years have brought us so 



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