166 THE NATURE AND ORIGIN OF LIFE 



Living bodies unlike crystals are always, so long as they are 

 living, under way of formation. At each instant of the life of 

 a cell its form is the result of an equilibrium established be- 

 tween its content and the surrounding medium. Only when 

 we have killed a cell by means of a fixative reagent (osmic 

 acid, bichloride of mercury), does its form become definitive 

 and transportable independently of external conditions like a 

 crystal. 



Here there is a fundamental difference between the form 

 of living bodies and that of crystals. This difference evi- 

 dently attaches to the fact that the colloid protoplasm is not 

 solid like the crystal and is not capable of a form independent 

 of the media through which it passes. 



And yet, in many cases, living bodies seem to have as 

 fixed a form as the hardest crystal. This comes from the 

 existence of the skeleton. 



Let us take protoplasm which for a long time is subjected 

 to constant conditions and in which, consequently, morpho- 

 genic factors that also remain the same build up a constant 

 form. Now suppose in the midst of such protoplasm a pre- 

 cipitation of solid substances (reserves, excrementitial sub- 

 stances) which agglomerate with each other to form a resist- 

 ing cage that imprisons the whole colloid substance. The 

 skeleton, thus built up by the living being itself, will be 

 henceforth carried along with it through all the media which 

 it traverses and will be a new morphogenic factor. Such a 

 factor may even become so important that all others disappear 

 before it and we no longer have an active protoplasm, creator 

 of forms in the environing conditions, but a passive half- 

 liquid clothing a solid skeleton as the waffle-paste covers the 

 waffle-iron or, more simply, as water in a bottle takes the 

 bottle's form. 



