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after liaviiii!;- exerted its action on protoplasm for a 

 relatively long time. We encountered in the literature 

 a few reports of rapid injury by cold. The mechanism 

 of injury is apparently different in these two cases; a 

 slow injury suggests a disturbance in the interplay of 

 physiological functions while a rapid injury is more likely 

 to be due to some sudden structural changes such as 

 precipitation, solidification, etc. The two cases will be 

 treated here separately. 



1. Sloir IiiJiirioKS Action. A. Observations. Ho- 

 moiotherms enter into a state of coma when their body 

 is cooled to some temperature above zero and they are 

 killed on further cooling. 



A state of rigor, induced by chilling, has been de- 

 scribed in homoiotherms and poikilotherms, in particular 

 in fishes. 



The numerous observations made on insects, either in 

 the adult or in the larval stages, are contradictory. Both 

 a high resistance and a high sensitivity to cold have been 

 reported (cf. Bachmetjew, 1901 and 1907, and Uvarov, 

 1931). 



Prolonged exposure of some plants to near-zero tem- 

 peratures is sometimes fatal. 



In general, organisms adapted to high temperatures 

 are more easily affected by cooling. Among these one 

 should mention, besides the tropical plants, some poikilo- 

 therms, in particular reptiles. 



While the plants and animals just mentioned are higher 

 forms, less differentiated or undifferentiated protoplasm 

 has also been reported to be injured or killed by cold 

 without freezing. Eggs are, according to some authors, 

 very sensitive: ant eggs ( Pictet, 1893), eggs of the Med- 

 iterranean fruit fly (Bach and Pemberton, J. Agr. Res., 

 5, 657, 1916), bedbug eggs (Hase, Ztschr. f. Parasitenk., 

 2, 368, 1930), chicken eggs (Moran, 1925). However, 

 there are also reports claiming a high degree of resis- 

 tance to cold in eggs. 



