4S 



the lliiid (l('('iin.-il ))l;ic(' li;i\c aimiscd some lalfr iiiN'csti- 



Maximow (li)14) reiieatcd tlic exporiments of Apclt, 

 also using- plasmolysis as a criterion of vilalily. He 

 obtained the follow! iii;- i-csulls: 1. Potato tissue frozen to 

 -2.11° (internal tenii)('ra1ui-e) had all its cells alive after 

 thawing-; 2. The num])er of dead cells was quite consider- 

 able after freezing to - 2.26° ; 3. The cells were practically 

 all dead at -2.66°. The death temperatures would then 

 lie in the neighborhood of - 2°. 



In other experiments, ^Maximow (11)14) showed that the 

 velocity of freezing was a factor to be considered in the 

 problem of death temperatures. A piece of potato, frozen 

 to -1.82° in 13 minutes, had almost all its cells alive; 

 another, frozen to the same temperature in 3 hours 52 

 minutes, had most of its cells dead. Measuring then the 

 amount of ice formed before death occurred he came to 

 the conclusion that a slower freezing, in the second experi- 

 ment, had caused more water to freeze in the tissue, and 

 that death depends, in the last analysis, on the quantity 

 of ice formed. These results fit with the notion of the 

 death point, according to which death is conditioned by 

 a number of variable factors and does not take place 

 Avithin sharply defined temperature limits. 



Luyet and Condon subjected to slow freezing in an air 

 chamber potato tissue cut into cylindrical shells having a 

 wall thickness of 2 mm. and slipped around the bulb of a 

 thermometer; they stopped the cooling process in suc- 

 cessive experiments, after congelation had proceeded for 

 various lengths of time and they counted the number of 

 living cells, using the plasmolysis test combined with a 

 vital staining method. They found that as long as the 

 freezing cui-ve stays at an appi'oximately constant hori- 

 zoiilal level, in genei-al above - 2°, the cells are pi-aciically 

 all alive even after a freezing- of 12 to 15 minutes. Death 

 begins when the temperature drops below - 2°, and, if cool- 

 ing is continued at the same slow rate, the death of all the 

 cells requires about 10 moi-c minutes; Ihe temperature, 



