XIV.] LIVING MATTER AND ITS EFFECTS. 223 



piece of jelly swells by taking in water. And the primitively 

 single cell becomes a cell-aggregate, not by attachment of 

 strange cells, from without, to that which first existed ; but, 

 by the growth and division of the primitive cell ; and the 

 repetition of the processes of growth and division in the 

 successive generations of new cells thus produced. 



There is another very striking difference between the 

 growth of such not-Hving bodies as may be said to grow, 

 and living growth. A crystal can grow, only if the materials 

 of which it is composed exist, as such, in the liquid which 

 surrounds it. A crystal of salt can grow only in a solution 

 of salt ; and a crystal of sulphate of soda, in a solution of 

 sulphate of soda. 



It is quite otherwise with a plant. A single pea may not 

 only develop into a large pea-plant, but may ultimately 

 give rise to a multitude of peas as large as itself In other 

 words, the pea, in the course of its development, accu- 

 mulates within itself many hundred times the quantity of 

 protein compounds, of cellulose, of starch, of sugar, of fat, 

 and of water and mineral salts^ which it primitively contained. 

 Nevertheless, of all these bodies, it is certain that none but 

 the water and the mineral salts exist, as such, either in the 

 air or in the soil. In fact, strange as it may seem, the soil 

 is a superfluity. A pea will grow into a perfect plant and 

 produce its crop of peas, if it is supplied with water contain- 

 ing nitrate of ammonia and the phosphates, sulphates, and 

 chlorides of potassium, calcium, iron, and the like, which it 

 needs, and is freely exposed to the air and to sunshine. Under 

 such conditions as these, it is obvious that the full-grown plant 

 must be almost entirely composed of fluids and gases which 

 have been transmuted into solid matters ; and that it has 

 manufactured the multifarious, and often highly complex 

 chemical compounds, of which its body is composed, 



