298 LIFE AND DEATH. 



liquor, the whole of the excess immediately passes 

 into the state of a crystallized mass. The first 

 crystal has engendered a second similar to itself; 

 the latter has engendered a third, and so on from one 

 to the other. If we compare this phenomenon with 

 that of the rapid multiplication of a species of 

 microbes in a suitable culture medium, no difference 

 will be perceived. Or perhaps we may note one 

 unimportant difference — the rapidity of the propaga- 

 tion of the crystalline germs as opposed to the relative 

 slowness of the generation of the micro-organisms. 



Again, the propagation of crystallization in a super- 

 saturated or superfused liquid may be delayed by 

 appropriate devices. 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 filled with 

 sulphur in a state of superfusion 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. 



Sterilization of Crystalline Media and Living Media. 

 — Ostwald varied these experiments by using salol. 

 He melted the substance by heating it above 39°.5 C; 

 then, protecting it from crystals of any kind, he let 

 the solution stand in a closed tube. The salol re- 

 mained liquid indefinitely — until it was touched with 

 a platinum wire that had been in contact with solid 

 salol — i.e.y until a crystalline germ was introduced. 

 But if the platinum wire has been previously sterilized 

 by passing it, as the bacteriologists do, through a 

 flame, it can then be introduced into the liquor with 

 impunity. 



