WHAT IS PHYSICAL LIFE 



make it a mechanism. Very far from it. 

 We might reduce a watch to powder with- 

 out the least loss of its materials, but then 

 we would not have the watch any more. 

 So a living mechanism is not the same 

 with its component materials, but justifies 

 our speaking of it as a living mechanism 

 only when its parts are adjusted to each 

 other with a fitness which is beyond that 

 of any non-living mechanism in the world. 

 We shall see that there is no fitness like 

 a living fitness. 



A great steam engine, for example, is 

 not near as complex, nor does it require 

 a tithe of the adjustments of its parts 

 with one another, which are necessary in 

 a human eyelid. Not counting the lach- 

 rymal gland and its appendages, an eyelid 

 of ours is anatomically made up of at 

 least forty-eight different structures and 

 special arrangements of tissues, any one 

 of which, if it did not fit in with the rest, 

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