334 



SENSITIZATION TO HEAT 



Experiment 4 was made in order to determine whether or not we 

 are deahng with an additive effect instead of heat sensitization. 



Sensitization Experiment. 



Experiment 5. Effect of Radiating First and Then Heating. — Or- 

 ganisms were radiated for 4 seconds at 17-18°C. and then exposed 

 on a temperature slide to 24-26° C. for 60 seconds. 



Total No. of organisms radiated 44 



No. of deaths 29 



Per cent of death 66 



Summary. 



Experiment 

 No. 



Treatment. 



Radiation alone 



Extra manipulation 



Heat alone 



Heating first then radiating. 

 Radiating first then heating. 



Deaths. 



per cent 







10 







8 



66 



In a previous paper^ it has been shown that Paramecia recover in 

 1 hour from the effects of a 4 second exposure to fluorite rays, so that 

 an additional 4 second exposure does not increase the effects of the 

 first. 



We were interested to see whether the organisms would likewise 

 recover from the heat sensitization caused by an exposure of 4 seconds 

 to fluorite rays. In the following experiments the organisms were not 

 exposed to the higher temperatures immediately after radiation, but 

 in order to permit recovery to take place were kept at the radiation 

 temperature for varying periods of time. 



Recovery Experiments. 



Experiment 6. Recovery Period ^ Hour. — Organisms were radiated 

 for 4 seconds at 17-18°C., and after \ hour at 17-18°C. were exposed 

 on a temperature sHde to 24-28°C. for 60 seconds. 



