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//. 1\ () 1 (' r 1 ;i y (' (I I) y S u h c o o 1 i ii <•• i ii 

 X a 1 II r e. Conceriiiiig Iho role j)lay('<l by subcooliiiji: in 

 the preservation or in the injni-y of j)hints and animals 

 in natnre, a review of the literature I'eveals that the most 

 diverse views have been held. These views depend on the 

 theory accepted by each individual author for the mechan- 

 ism of death by cold. They are, too often, rather theo- 

 retical and lacking in ex])erimental evidence. 



Since the generality of investigators have found that 

 protoplasm is not injured in the subcooled state, they nat- 

 urally concluded that subcooled animals or plants are 

 "protected" against the damage of frost. The resistance 

 of plants in winter to temperatures of several degrees 

 below zero is often attributed to a tendency to subcool. 

 The fact that trees in northern forests and poikilotliermic 

 animals in cold climates are not killed by long and severe 

 winters is also thought by many to be due to a particular 

 ability to undergo deep subcooling (Kalabnchov, per- 

 sonal communication). 



Weigman (1936) pointed out that hibernating snails 

 have a freezing point as high as -0.39° ; their survival to 

 low temperatures therefore cannot be attributed to a low^- 

 ering of the freezing point at the onset of the state of 

 dormant life, it must then be due to the ability to sub- 

 cool, 



Harvey (1919) suggested another indirect protective 

 role of subcooling, namely, that plants left for some 

 length of time in the subcooled state might undergo adap- 

 tative changes and become hardened against frost. 



The authors who held the theory of the specific mini- 

 nmni (see below) according to which death occurs at a 

 certain given temperature, no matter whether ice is 

 formed or not, took sides against the view of ''protective" 

 subcooling. For them, only that which prevents an organ- 

 ism from reaching the specific minimum is protective. 

 Subcooling itself does not, of course, prevent the drop 

 of temperature, while freezing, by liberating heat, does. 



