458 WHEELER P. DAVEY 



SUMMARY 



1. It has been shown that the hfe of TriboUum confusum may 

 be prolonged by the use of a purely physical agent, i.e., x-rays. 



2. The prolongation of life due to a series of small daily doses 

 is greater than that of larger doses given all at once. 



3. The lethal effect of an x-ray dose is less if it is split up into 

 a series of small daily doses than if it is given all at once. 



4. A method of graphical analysis of results has been de- 

 scribed by which the number of causes of death may be de- 

 termined from the death rate, and by which the effect of an 

 external agent upon each of these causes may be studied. 



5. Using the same kind of organism throughout the whole 

 experiment, the work reported in this and the previous paper 

 has shown that, by merely varying the size of the dose, a purely 

 physical agent (x-ray) may be made to produce at will, 1) a 

 stimulation; 2) a destructive effect which occurs only after a 

 latent interval, and 3) an instant destructive effect. 



Research Laboratory, 

 General Electric Co., 

 Schenectady, N. Y. 



