426 THE LIFE OF MATTEE. 



a suitable culture medium, but one important difference will be per- 

 ceived — the extreme rapidity of propagation of the crystalline germs 

 as opposed to the relative slowness of the generation of the micro- 

 organisms. 



The crystalline individual gives birth, then, to another individual 

 that conforms to its own type, or even to varieties of that type when 

 such exist. Into the right branch of a U tube tilled with sulphur in a 

 state of surfusion Gernez dropped octahedric crystals of sulphur, and 

 into the left branch prismatic crystals. On either side were produced 

 new crystals conforming to the type that had been sown. 



StcrHizatloii of eryiitallme media and living mtdia. — Ostwald varied 

 these experiments with salol. He melted the substance by heating it 

 above 39.5° CI; then, protecting it against an}- crystals, he let the 

 solution stand in a closed tube. The salol remained liquid indefi- 

 nitely — until it was touched with a platinum wire that had been in 

 contact with solid salol; that is to say, until a crystalline germ was 

 introduced. But if the platinum wire has been previously sterilized 

 after the manner employed l)y l)acteriologists, l)y passing it through 

 a flame, it can then be introduced into the liquor with impunity. 



The dimensions of cryst(dline gernis are voinparahle to those of 

 iiiicrohes.—'SVe may dilute the solid salol with an inert powder — sugar 

 of milk, for exanqjle — dilute the tirst mixture with a second, the sec- 

 ond with a third, and so on; then, throwing into the solution of sur- 

 fused salol a tenth of a milligram from one of these various mixtures, 

 we And that the production of crystals will not take place if the frag- 

 ment thrown in weighs less than a millionth of a milligram or meas- 

 ures less than ten thousandths of a millimeter on a side. It would 

 seem, then, that these are the dimensions of the crystalline particle or 

 crystallographic molecule of salol. In the same way Ostwald became 

 assured that the crystalline germ of hyposulphite of soda weighs 

 about a billionth of a milligram and measures a thousandth of a nuUi- 

 meter; that of chlorate of soda weighs a ten-millionth of a milligram. 

 These dimensions are entirely com[)arable with those of microbes. 



All these phenomena have been studicnl with a detail into which it 

 is impossible to enter here, and which cleai'ly shows more and more 

 clos(^ analogies between tlu^ formation of crystals and the generation 

 of micro-organisms. 



Extension and ][yiro'pagation of crystallization — Optimum, tempera- 

 ture of inciibation. — Crystallization which has commenced around a 

 germ is propagated more or less rapidly and ends by in\ading the 

 entire liquor. 



The rapidity of this movement of extension depends upon the con- 

 ditions of the environment, particularly u])on its temju'rature. This 

 is shown very well by the experiments of Tannnann with betol. This 

 body, a salicylate of naphthyl. fuses at 9(1' C. If it is meltonl in tubes 



