CHEMICAL CHARACTERS OF CELL 77 



it builds and rebuilds its own substance, bend- 

 ing the materials which it assimilates to its 

 own uses and purposes. This process of assimi- 

 lation is no doubt in some measure chemical, 

 that is to say chemical changes and operations 

 take place during its progress. But when one 

 says so much, one is not saying that the changes 

 are purely chemical, for such, in fact, is not 

 the case. In the course of an ordinary chemical 

 combination two or it may be more sub- 

 stances unite to form a third, as common salt, 

 for example, is formed from sodium and hydro- 

 chloric acid. But the cell takes up not-living 

 matter and assimilates it and converts it into 

 living protoplasm. Moreover this process of 

 growth is interstitial in its character and not 

 superficial, in other words it is not a growth 

 in size due to the deposition of new layers on 

 top of the old ones, as in the case of a rolling 

 snowball. The deposition of new material 

 occurs throughout the entire substance of the 

 cell, so that its increase in size is due to a 

 general expansion of the entire organism. And 

 herein lies a prime difference between the living Crystals 

 organism and a crystal, forms between which at \ d living 

 some have urged that a close resemblance 

 exists, or at least have argued that between 

 crystallisation and assimilation there were 

 sufficiently close resemblances to permit it to 



