§3] TEMPERATURE-LIMITS OF LIFE 241 



later. As a result of these and others' investigations we may 

 conclude : Protoplasm may under certain circumstances, of 

 which one of the most important is the absence of water, resist, 

 uninjured, the lowest temperatures. There is no fatal minimum 

 temperature for dry protoplasm. 



We must now turn our attention to those cases in which the 

 phenomena of cessation of activity or death appear, and seek 

 to determine their causes ; and first concerning temporary 

 cold-rigor. We have already seen that as the temperature is 

 lowered, the rate of metabolic processes and protoplasmic 

 movements is lowered. What happens at the lower limit of 

 activity, and where does this lie? The chlorophyll granules 

 of Vallesneria move (according to Veltbn) only about 1 mm. 

 per minute at 1° C. and not at all at 0°; the rotation of Nitella 

 ceases (Nageli, '60, p. 77) at 0° C. ; in Tradescantia hairs, 

 movement is wholly arrested on freezing the cell sap (Kuhne, 

 '64, p. 100, and Demooe, '94, p. 194). Even in seeds and 

 bacteria, which are not killed by the lowest temperatures, all 

 vital activities have probably ceased at 0°, for de Candolle 

 ('65) found that in only one species out of ten could he get a 

 seed kept at 0° to germinate, and even then germination was so 

 retarded that it took from 11 to 17 days as opposed to 4 days 

 at 5.7°. Likewise, bacteria do not multiply below +5° to 

 + 10° (BoNARDi and Gerosa, '89). Among animals, Kuhne 

 ('64, p. 46) found Amoeba cooled to near 0° almost motionless. 

 Purkinje and Valentin ('35) first noticed that the ciliated 



experiments on Scolopendra, lie merely says: "I have frozen to —40° three 

 Scolopeudras which perfectly resisted the treatment and lived after thawing out. 

 Submitted to — 50°, they have also resisted. Frozen a third time to — 90°, they 

 are all three dead." Now, in the absence of further data, it is quite possible 

 that the heat of metabolism kept the internal body temperature considerably __ 

 above that of the chamber, the thick cuticula preventing rapid loss of heat, very 

 much as a man's clothing enables him to withstand the — 40° of an arctic winter. 

 Another experiment of Pictet's lends greater probability to this explanation of 

 some cases of great resistance. Three snails were subjected to a temperature of 

 from — 110° to — 120° during several days. The operculum of two of these was 

 not intact, so that it did not close the orifice. These two individuals died ; but 

 the third, which was completely sealed up, survived. Those which were not 

 sufficiently clad, so to speak, lost so much internal heat that their internal fluids 

 were frozen. Of course this criticism cannot apply in the case of those organ- 

 isms mentioned in the text which are without a thick cuticula. 



