224 



Altliougli IIktc ai"(' several unexplained exeepi ions, llic 

 results obtained in the \it riticalion of pr<)1()i)lasm, and in 

 l)artic'iilar those fiii'nisiied l)y moss, e])idermal cells and 

 muscle fibers, seem lo conlirui llie view thai a s;ood vitri- 

 ficatiou is not injurious, there Ix'iui;' no molecular dis- 

 turbance, while an incomi)lele vitrification or devitrifica- 

 tion and, (I forfiori, cryslallizaliou, are injurious to the 

 extent tliat they disrupt the living structure. 



SimiMARY 



1. At different temperatures, matter can exist in four 

 physical states: as a gas, as a liquid, as a crystal and as 

 a glass. The last-named state occupies the lowest zone in 

 the scale of temperatures. 2. Crystallization is possible 

 only within a limited range of temperatures. Below this 

 range, matter is too inert to crystallize (in other words, 

 too cold to freeze). 3. The vitreous state is obtained by 

 cooling a liciuid very rapidly. The rapidity has for its 

 object to make the liquid traverse the zone of crystalliza- 

 tion temperatures before it has the time to become crystal- 

 line. 4. By using, as a method of rapid cooling, the immer- 

 sion in liquid air of material previously reduced to thin 

 layers, we vitrified solutions of various organic and inor- 

 ganic substances, such as gelatine, albumin, amino acids, 

 agar, gums, dextrin, sugars, glycerine, formaldehyde, 

 sodium chloride, sodium hydroxide, etc. 5. The more 

 dilute a solution is, the more difficult it is to vitrify it. 

 Pure water could not be vitrified by our methods. 6. A 

 vitreous substance devitrifies, that is, crystallizes, when 

 one raises its temperature. One can therefore cause the 

 crystallization of a body by warming it up from the vitre- 

 ous state. 7. The temperatures of devitrification of solu- 

 tions rise when one passes from a solute of simple molecu- 

 lar composition to a more complex one, in the same series. 

 8. At high concentrations of a given solute (for example, 

 one molecule of sucrose for 9 or 10 of water), devitrifica- 

 tion does not take i)lace. At intermediate concentrations 

 (one molecule of sucrose for 10 to 14 of water), devitri- 



