271 



only if they had not been exposed to too low a tem- 

 perature. 



Iljin (11)34) revived the old theory of injury and 

 death by too rapid thawing and established it on a new 

 basis. He observed that when, during freezing, water 

 is extruded by osmosis from the vacuoles of plant cells, 

 the protoplast contracts and the opposite sides of the 

 cytoplasmic sac approach each other and come in con- 

 tact in the center of the cells, while they are still sepa- 

 rated by cell sap in the outer portions. On thawing, 

 water suddenly invades the contracted protoplast and 

 tears it, if it cannot pull apart the adhering sides. The 

 author says that he observed the same phenomenon, 

 namely that the protoplast tears open, in too rapid 

 deplasmolysis. In the case of death by desiccation he 

 claims to have evidence that injury results from the too 

 rapid invasion of the protoplasm by water on remoist- 

 ening. In his experiments on low temperature effects 

 he succeeded in saving from death cells of red cabbage 

 frozen at the temperature of solid carbon dioxide. His 

 method consisted in slowly restoring the water to the 

 cells by letting cooled hypertonic solutions of sugar, gly- 

 cerine or hiorganic salts of gradually decreasing con- 

 centrations fall dropwise on the frozen sections of the 

 tissue. 



Of the few authors who found slow thawing more in- 

 jurious than rapid thawing we shall mention here a re- 

 cent work of Turner and Brayton (1939) on the spiro- 

 chetes of relapsing fever. When rewarming and thaw- 

 ing took place in 30 seconds, (in water at 37°) or in 25 

 to 35 minutes (at room temperature), there were living 

 spirochetes. As a test of vitality the authors used 

 motility and pathogenicity for mice. 



The numerous data recorded in this section do not 

 allow one to draw any general conclusion. It is prob- 

 able that the etfects of slow thawing are different in 

 different organisms, as a comparison of the results on 



