12 



Goeppert 1 was among the first to make a careful study of killing 

 from cold. He observed the formation of ice within the cells, and 

 also in the intercellular spaces. Sachs 2 found that it was almost always 

 in the latter. 



Miiller-Thurgau 8 in his very excellent studies found that when 

 the ice crystals were found within the cells, it was due to very rapid 

 freezing such as Goeppert used, and when the temperature was low- 

 ered very slowly, ice crystals were seldom found within the cell. 

 Miiller-Thurgau proved that ice formation within the tissue is neces- 

 sary to freezing to death. It is well known that a liquid may often 

 be supercooled several degrees below the freezing point before ice 

 formation begins. He observed that this often occurs in cooling 

 plant tissue in the laboratory, and when pieces of tissue (potato) 

 were supercooled, if they could be warmed without ice formation 

 they were not injured, while if ice formed they would kill at a higher 

 temperature than that to which they were supercooled. Voigt- 

 lander measuring his temperatures with more delicate apparatus, 

 has proved this perhaps more conclusively. When he supercooled 

 tissue to four or five degrees centigrade below the point at which it 

 would kill when ice formed, if the temperature could be raised to 

 above the freezing point without ice formation, killing never occurred. 

 It was held by many scientists, at the time of Miiller-Thurgau 's 

 first work, as well as by a large majority of practical observers, that 

 death was due not directly to low temperature, but to rapid thawing. 

 Goeppert was of the opinion, however, from his studies, that the 

 killing was a direct result of freezing and that death actually occurred 

 before the thawing began. Sachs, from some experiments with 

 plants immersed in cold water to thaw, after freezing, held that 

 the amount of killing of the plants at any given temperature was 

 determined by the rate of thawing. Miiller-Thurgau showed that 

 the method used by Sachs of thawing plants in cold water was not 

 a method of slow thawing, but rather a very rapid thawing since a 

 layer of ice crystals would form on the outside of the tissue, giving 

 off heat that would thaw the tissue very rapidly. In fact the tissue 

 thawed in cold water much more rapidly than in the air at room 

 temperature. 



Miiller-Thurgau using a large number of plants, thawing them 

 from the same temperature, some rapidly and some more slowly, 



■Ueber die Warmeentwickelung, etc. Book. 1830. (Bibl. No. 44). 

 *Ber. u. d. Ver. d. Kon. Sachs. Gesell. d. Wlss. zu Leipzig, 1860, Vol. 12, pp. 1-50. (Bibl 

 No. 94). 



"Landw. Jahrb. Vol. 15, p. 453, 1886. (Bibl. No. 78). 



