saiiu' ninouiit of water crystallizes each time, at the same 

 initial freezing; point. This shows that no irreversible 

 alteration takes place from one freezinj;- to the other. 

 In the case of livin.ii' tissues, on the contrary, the freezing 

 l)oinl is raised 1>\' a lirst lethal freezing and the ([uantity 

 of water which crystallizes at a gi\-en temperature, in 

 a second congelation, is different from the (juantity 

 solidified in the first. 



Several authors have assumed that, at death, pro- 

 teins are denatured in a salt solution which became con- 

 centrated by freezing. Concerning this theory, as applied 

 to nmscle proteins, Moran (1929) remarks that all at- 

 tempts to produce synthetically a solution of the same 

 composition as the fluid of the muscle have failed and he 

 attributes this failure to the fact that the calcium is not 

 simply in solution in the living muscle but that it is 

 associated with the proteins. This remark suggests the 

 hypotliesis that the destruction of the complex, protein- 

 calcium, might constitute death by cold. 



SUMMARY 



1. Death in frozen animals or plants has been attributed 

 by some pioneer authors to a withdrawal of energy and 

 the resulting impossibility on the part of the cooled or- 

 ganism to supply the energy necessary for vital activities. 

 2. According to this theory freezing is impossible as 

 long as the organism is alive; life has to be destroyed to 

 allow the formation of ice. 



3. Other investigators have attributed death of frozen 

 plants to the attainment of a given minimal temperature, 

 characteristic of each species. 4. Accordingly, when this 

 '^specific minimal temperature" is l)elow the freezing 

 point, the formation of ice protects against injury and 

 death, while subcooling is dangerous. 



5. Death has been attributed to a mechanical injury 

 consisting in a bursting of the cells by the expansion of 

 the ice in formation; but the ru])turing of cells after slow 



