THE EFFECTS OF HEAT AND RADIANT ENERGY 107 



found in cheese are killed in one minute at a temperature of from 80 

 to 90; while for the spores of the same bacillus a temperature 

 of from 105 to 120 was required.* 



Duclaux has called attention to a fact which is of importance for 

 the investigation of the upper temperature limit for the life of organ- 

 isms. According to this author it is erroneous to speak of a definite 

 temperature as a fatal one, instead we must speak of a deadly tem- 

 perature zone. This is due to the fact that the length of time which 

 an organism is exposed to a higher temperature is of importance. Du- 

 claux quotes as an example a series of experiments by Christen on the 

 spores of the bacilli of the soil and of hay. The spores were exposed 

 to a stream of steam and the time determined which was required at 

 the various temperatures to kill the spores. 



It took at 100 .... over sixteen hours. 



" " 105-110. . . . two to four hours. 



" "115 . . . . thirty to sixty minutes. 



" " 125-130. . . . five minutes or more. 



" "135 one to five minutes. 



" " 140 .... one minute. 



In warm-blooded animals 45 is generally considered a temperature 

 at which death occurs in a few minutes; but a temperature of 44, 

 43, or 42 is also to be considered fatal with this difference only, that 

 it takes a longer time to bring about death. This fact is to be con- 

 sidered in the treatment of fever. 



It is generally held that death in these cases is due to an irreversible 

 heat coagulation of proteids. According to Duclaux, it can be directly 

 observed in microorganisms that in the fatal temperature zone the 

 normally homogeneous, or finely granulated, protoplasm is filled with 

 thick, irregularly arranged bodies, and this is the optical expression of 

 coagulation. The fact that the upper temperature limit differs so 

 widely in different forms is explained by Duclaux through differences 

 in the coagulation temperature of the various proteids. It is, e.g. 

 known that the coagulation temperature varies with the amount of 

 water of the colloid. According to Cramer, the mycelium of Peni- 

 cillium contains 87.6 water to 12.4 dry matter, while the spores have 

 38.9 water and 61.1 dry substance. This may explain why the myce- 

 lium is killed at a lower temperature than the spores. According to 

 Chevreul, with an increase in the amount of water, the coagulation 

 temperature of albuminoids decreases. The reaction of the proto-- 



* Duculax, Traite de microbiologie, Vol. I, p. 280, 1898. 



