261 



ample, a clear disliiiction hetweou the theory of death 

 by withdrawal of energy and that of death at a tem- 

 perature minimum and he rejected the former as con- 

 tradicted by the following facts. Cells of potato tubers 

 were not killed in one hour at a temperature 0.3 to 0.4 

 degree higher than that which was instantly lethal, 

 neither were they killed in two hours at a temperature 

 one degree higher than the death point. Death, then, 

 is not attributable to a withdrawal of energy, since the 

 same amount of energy could be withdrawn in a longer 

 time at a higher temi)erature as in a shorter time at a 

 lower temperature. Retaining the theory of the specific 

 minimum, the author thinks that a protoplasmic disor- 

 ganization when the temperature reaches that minimum 

 constitutes the mechanism of death. 



III. THEOKV ATTRIHUTING DEATH TO MECHANICAL 



INJURY 



Death has been considered as resulting in various ways 

 from a mechanical injury inflicted during freezing or 

 thawing. A. Some authors have thought that the expan- 

 sion of ice during its formation bursts the cells, as it 

 bursts a bottle filled with water ; B. Others have assumed 

 that the ice crystals in the cells or in the intercellulars 

 damage the protoplasm or the cell parts by piercing or 

 tearing them; C. Some investigators have invoked the 

 pressure exerted by the expanding ice as the cause of 

 death, its action being not to burst the cells, but to 

 compress the protoplasm; D. A few biologists have at- 

 tributed death to a mechanical injury inflicted, not by the 

 ice itself, but by the jarring of the protoplast during 

 plasmolysis and deplasmolysis, as a result of which the 

 cytoplasmic mass would be torn off from the cell walls 

 where it adhered. 



A. Most of the reviewers have attributed to Duhamel 

 and Buffon the idea that death results from a mechanical 

 injury caused by the expanding ice in living tissues. We 



