422 THE LIFE OF MATTER. 



VI. 



NUTRITION IN THE LIVIN(I BEING AND IN THE CRYSTAL. 



It has been said with justice tliat the property of nutrition may be 

 considered as the most characteristic and essential one of living- beings. 

 Such beings are in a state of continual exchange with the surrounding- 

 medium. They assimilate and disassimilate. By assimilation the 

 substance of their })eing increases at the expense of the surrounding- 

 alimentary matei'ial, which is rendered similar to that of the being 

 itself. 



Af<x!iiill<ition and (jrointh in the cryxtal. — There exists in the crystal 

 a property analogous to nutrition, a sort of nutrility, Avhich is the 

 rudiment of this fundamental property of living beings. The develop- 

 ment of a crystal starts from a primiti\'e nucleus, the germ of the 

 crystalline individual that we will shortly conjpare to the ovum or 

 embryo of a plant or an animal. Placed in a suitable culture medium — 

 that is to say, in a solution of the su))stance — this germ goes on to 

 develop. It assimilates the matter in solution, incorporates the parti- 

 cles of it, and increases, preserving at the same time its form, repro- 

 ducing its 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 properly nourish it — we might say, to purvey to it. 

 Very frequently, 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 can not be nourished, 

 the crystal, arrested in its growth, assumes a state of rest which is not 

 without analogy with that of a seed or of a revivified animal. It 

 awaits the return of favorable conditions, the l)atii of solu])le matter, 

 in order to resume its evolution. 



The crystal is in a relation of continual exchang«Mvith th(> surround- 

 ing medium, which feeds it. These exchang(\s are regulated l)v the state 

 of this medium, or, more exactly, ])y the state of the liciuid stratum 

 which is in inmiediate contact with the crystal. It loses or it gains in 

 su])stancc if, for example, that layer becomes heated or cooled more 

 ra})idly than it. In a general way it assimilates or disassimilates 

 according as its environment is saturated oi- diluted. There is, then, 

 in this a sort of mobile eciuilibriuni. conq)arable, in some May, to that 

 of the living being. 



Methods of growth of the cnjdid and of tJie litung hehty — Intnssuscep- 

 tlon — Apposition. — In truth, there seems to l)o a complete opposition 

 between the crystal and the li\ ing- being as regards their mannei" of 

 nutrition and growth. The latter performs this by intussusception; 

 the former by appositicMi. The crystalline individual is all surface. 

 Its mass is impenetrabh^ to the nutritive materials. Since only the 



