1 68 



CHARLES PACKARD. 



cumb much more quickly than at low temperatures. The results 

 are shown in the accompanying figure. An analysis of the curve 

 shows that for each increase of about 8 C. the length of the 

 lethal dose is halved. The curve is thus similar to that which 

 expresses the relation between temperature and the velocity of a 

 great number of reactions both inorganic and physiological. 



Hours of 



345 



Radiation 



678 



10 



TEXT-FIGURE i. The effect of temperature on susceptibility. 



Snyder (8) cites more than fifty physiological reactions which con- 

 form to this type of curve : Woodruff and Baitsell (9) show also that 

 the division rate of Paramcecium aurelia varies similarly with 

 changing temperature. 



The cells were not injured by these temperatures alone. While 



