18 GENERAL BIOLOGY 



each other as well, and such a mechanism will run 

 correctly only when every part is in its proper 

 place and adjusted carefully to every other part with 

 reference to the joint action of the whole. 



It is so with protoplasm. However we may de- 

 fine life it is certainly true that the property of 

 protoplasm, by virtue of which it is " living matter," 

 is bound up in the interrelations of the various parts 

 composing it. And just as a machine must be 

 properly assembled, to use a technical phrase, so 

 protoplasm does not exist as living substance except it 

 be organized. Destroy or fundamentally alter this or- 

 ganization and, although we may get the same chem- 

 ical analysis of the material and the same weight 

 of substance, it is no longer alive. But it must be 

 noted that the comparison with the watch cannot 

 be pushed too far, for, unlike a rigid mechanism, 

 protoplasm is extremely plastic and capable of 

 adjusting itself to very wide ranges of structural 

 alteration without ceasing to be alive. Indeed the 

 living organism is constantly so adjusting itself 

 in response to external conditions, a phenomenon 

 which many hold to be the fundamental and charac- 

 teristic fact of life itself. 



The Cell. - - The difference between an oak leaf 

 and a waxen image of one is not alone a difference 

 in the chemical substances composing the two. 

 Should we cut a thin slice from the wax leaf and 

 examine it under a microscope we could distinguish 

 nothing to mar its homogeneity. Should we do 



