28G 



/. Plii/sioJdfiicdJ (li(nif/es. A weaken iiii;- of vitaliiy by 

 tlio action of colil (Ui ])roto])lasm lias l)een assumed by 

 Irnischor (1912) to oxi)lain liow a ])rolon<;-ed or repeated 

 exposui'e causes a ,ni'a<luall\' inci-casini^' (bunage. He had 

 observed that some moss species whicli resisted one freez- 

 ing at "20 were killed by 4 fi'eezings at 15' and that 

 moss which was not entii-ely killed l)y one freezing at 

 — 1") , this temperature being maintained for IS hours, 

 died entirely after an ex])osure of 4 days to - 10 . (Sim- 

 ilar experiments were reported by numerous other au- 

 thors, in particular by Goeppert, 1830, on Lamiiim and 

 by Ai)elt, 11)07, on ])otat()). 



Schaffnit and Liidtke ( 1932), who studied the influence 

 of low temperature on the metabolism of plants subjected 

 to various diets, came also to the conclusion that before 

 death there is evidenc«' of a gradual weakening under the 

 action of cold. Death would then be due, finally, to dis- 

 turbed metabolism. 



To assume that low temperature weakens protoplasm 

 and renders it more vulnerable to cold is in direct oppo- 

 sition with the observed fact that low temperature hard- 

 ens against cold. 



According to Krebs (1931), the muscles would lose 

 their ability to synthesize glycogen and phosphagen 

 after being frozen. Death would then occur when the 

 energy demands exceed the supply. 



Cold injury might be related to physiological changes 

 which take place at some particular temperature. Moran 

 (1925) cites, as an example of a change of the kind 

 which might be invoked here, the observation of Vernon 

 (,//. of Physiol, /7, 277, 1894) and of Castle {Jl Gen. 

 Physiol., 7, 189, 1924) that respiration in the frog and 

 in other animals and plants undergoes a critical change 

 at around +15 . It is possible that, in a similar man- 

 ner, some unknown activity, ])erhaps some enzymatic 

 process, is critically altered at the temperature at which 



