NUTRITION IN THE LIVING BEING. 39I 



specific type or a variety of it. Its growth proceeds 

 without interruption. The crystalline individual may 

 attain quite a large size if we know how to nourish it 

 properly — we might say, to fatten it. Very fre- 

 quently, at a given time, a new particle of the crystal 

 serves in its turn as a primitive nucleus, and becomes 

 the point of departure for a new crystal engrafted 

 upon the first. 



Taken from its mother liquor, placed where it 

 cannot be nourished, the crystal, arrested in its 

 growth, falls into a condition of rest not without 

 analogy to that of a seed or of a reviviscent animal. 

 Its evolution is resumed with the return of favourable 

 conditions — the bath of soluble matter. 



The crystal is in a relation of continual exchange 

 with the surrounding medium which feeds it. These 

 exchanges are regulated by the state of this medium, 

 or, more exactly, by the state of the liquid stratum 

 which is in immediate contact with the crystals. It 

 loses or it gains in substance if, for example, this 

 layer becomes heated or cooled more rapidly than the 

 crystal. In a general way, it assimilates or dissimilates 

 according as its immediate environment is saturated 

 or diluted. Here, then, we have a kind of mobile 

 equilibrium, comparable, in some measure, to that of 

 the living being. 



Methods of Growth of the Crystal and of the Living 

 Being. Intussusception. Apposition. — In truth, there 

 seems to be a complete opposition between the crystal 

 and the living being as regards their manner of 

 nutrition and growth. In the one case the method is 

 intussusception ; in the other it is apposition. The 

 crystalline individual is all surface. Its mass is im- 

 penetrable to the nutritive materials. Since only the 



