CHEMICAL CHARACTERS OF CELL 41 



it may be pointed out that when a crystal is formed 

 by the evaporation of the solution of some salt, 

 say the sulphate of copper which is formed into 

 the huge blue crystalline masses often exposed in 

 chemists' windows, what happens is that particles 

 of an identical chemical character come together 

 and take up for reasons, it must frankly be ad- 

 mitted, of which we are entirely ignorant the 

 characteristic form or any of the characteristic 

 forms of the crystals of the substance which was 

 in solution. So that a crystal is a mass of homo- 

 geneous particles, collected together and built up 

 into a regular edifice. Suppose we add new ma- 

 terial to this, with a view to increasing the size 

 of the edifice. All that happens is that new 

 material of a precisely similar character is added 

 layer by layer to the surface of the old, and this 

 new material must be identical in character with 

 that to which it is added. But in the cell, not 

 only is the addition not layer by layer but inter- 

 stitial and intimate, but also the substances which 

 are taken in are moulded to the purposes of the 

 cell and are broken up and converted into the very 

 substance of the cell itself or into bye-products of 

 one kind or another. Of this production of bye- 

 products more must be said in a further paragraph, 

 but before passing to the general question, it may 

 be well, as we engaged upon the topic of crystal- 



