223 



Water Content MetJiod Results 



More than 65% Slow devitrification Dead 



More than 65% Rapid warming Survival 



65% to 30% Slow devitrification Partly dead 



65% to 30% Rapid warming Survival 



Less than 30% Slow devitrification Survival 



Less than 30% Rapid warming Survival 



One sees that when the moss is sufficiently dried, it always 

 survives treatment by low temperatures, whatever be the 

 rapidity of cooling or of warming. When the water content 

 is high, the plants die if one lets them freeze, but survive 

 the vitrification if one prevents freezing by a rapid 

 warming. 



Finally we tried to vitrify muscle fibers (Luyet and 

 Thoennes, 1938c). Bundles of 6 to 10 fibers, taken from a 

 chloroformed frog and mounted on a metal frame, were 

 immersed in liquid air and then into Ringer's solution at 

 20°. The fibers so treated were thereupon placed on the 

 microscope and subjected to an electric shock. Some fibers, 

 often most of the fibers present, contracted. However, 

 they ceased to respond sooner than normal fibers to re- 

 peated electric shocks, and, for the same reaction, they 

 required an induction current of higher potential. But 

 whether the period of immersion in liquid air lasted several 

 hours or only a few seconds seemed to make no dilTerence. 



In a series of researches which we have just begun, we 

 intend to study the extent of the zone of crystallization in 

 various organic fluids such as muscle plasma, moss juice, 

 yeast extract, the protoplasmic fluid of the protozoa, etc. 

 Perhaps these researches will reveal the reason why cer- 

 tain living beings are very resistant to low temperatures 

 while others are not. The extent of the temperature inter- 

 val within which they freeze might be the determining- 

 factor in their sensitivity. Our first results on muscle 

 fibers seem to indicate that the temperatures at which the 

 muscle dies during devitrification are the same as the tem- 

 peratures of devitrification of muscle plasma, determined 

 by the method previously described for aqueous solutions. 



