CHAP. VIII 



Vitality 



137 



way by the suspended animation of a dried seed, which will 

 remain for years dormant, but ready when moistened to 

 spring into active life. 



How, then, are these substances built up into living 

 creatures ? Let us, that we may see this matter clearly, 

 think for a moment of the conditions of life of the simplest 

 creatures, the formless masses of living matter. All that 

 the simplest plants need is water" holding oxygen, carbonic 

 acid, and salts in solution. Out of these simple materials, 

 by the magic touch of their living bodies, they can build up 



the complex matter of which those bodies are made ; so that 

 they can grow and divide until there may be hundreds in 

 place of a single one. The image we must form of this 

 increase of living matter is that step by step substances of 

 an ever-growing complexity are made, one from the other, 

 until at last a substance so unstable is made that it begins 

 to break down into simpler forms of matter at the least 

 deviation from the precise conditions in which it was made, 

 and perhaps also with a ferment-like action causes changes 



