290 GENERAL PHYSIOLOGY 



In the light of these experiments the assumption that organisms 

 always perish when the living substance of the tissue-cells itself is 

 frozen solid, appeared very highly probable. But in opposition 

 to them recently Raoul Pictet ('98) has established facts in 

 accordance with which our ideas must apparently be wholly 

 changed. 



This well-known investigator, who has made a number of sur- 

 prising and extraordinarily valuable discoveries concerning the 

 chemical effects of very low temperatures, recently carried out in his 

 laboratory experiments upon the physiological effects of such 

 temperatures. The objects of his experiments were protected by 

 wood from contact with the metal walls of the cold vessel in which 

 fchey were placed, so that they were exposed to the low temperature 

 of the air only. It was thus shown that different animals behave 

 very differently. Fishes that were cooled down to -15° C. in a block 

 of ice remained living after careful warming, although others in 

 the same experiment could be ground to powder like ice. But upon 

 cooling to -20° C. the fishes died. Frogs endured without dying a 

 temperature of -28° C, myriopods -50° C, snails -120° C., and 

 bacteria even less than -200° C. In view of these surprising experi- 

 ments it can hardly be doubted that in individual cases the living 

 substance of cells can be frozen to ice without losing its capacity 

 of life. 



These phenomena suggest the question whether in frozen 

 organisms there is really a complete standstill of the vital pro- 

 cesses — a question that Preyer believes must be answered in the 

 affirmative. Theoretically, there is nothing opposed to this idea ; 

 for, when it is seen how with falling temperature the energy of 

 the vital processes constantly decreases, it must be believed that 

 in time a point may be reached where they cease altogether. 

 The possibility that the cell-liquid itself can freeze without abolish- 

 ing the vital capacity of the cell, would support this view ; for, as 

 has been seen, life cannot exist without water in the liquid state. 

 It would be expected therefore, that, as soon as the water in the 

 living substance has passed over into the solid state, the chemical 

 transformations in the cell would be at a standstill. But con- 

 clusive experiments for the decision of this question are thus far 

 wanting. If it should be established that living substance in the 

 frozen condition can be maintained for j^ears capable of life, just 

 as certain dried organisms can be so maintained for years, decades, 

 and even centuries, then the probability would approximate to 

 certainty that life in frozen organisms is really at a standstill. 

 At present this is not settled. One fact that is opposed to this 

 idea is the observation made by Pictet, that frozen organisms 

 cannot endure a farther fall of temperature beyond a certain 

 point. Upon thawing they cannot be revived. If life were really 

 at a complete standstill, it would be difficult to understand why 



