576 • WHEELER P. DAVEY 



certain latent interval; (3) to produce an instant destructive 

 effect.-i 



By analogy with the action of various drugs, one would expect 

 that the rays could be made to act in any one of these three ways 

 at will by merely varying the size of the dose. Not a sufficient 

 number of the authors cited above have adequately recorded the 

 dose to enable one to verify this analogy without further experi- 

 mentation. It is the purpose of this article to record the results 

 of experiments made toward this end. 



About a year ago the writer was engaged in some preliminary 

 work on the lethal effect of X-rays on Tribolium confusum. 

 These little beetles are ordinarily called "flour weevils" and are 

 said by Chittenden-- to be the most injurious enemy to prepared 

 cereal foods. In two years from the time of their recognition 

 as a distinct species they had spread to nearly every state in 

 the Union, and even as early as 1895 are said to have cost the 

 millers of the United States over $100,000 in manufactured prod- 

 ucts alone. It was found possible to destroy the eggs of these 

 beetles with X-rays, thus giving hope of a new technical use for 

 X-rays, but the most interesting results from a scientific point 

 of view were obtained from the beetles themselves. 



PRELIMINARY EXPERIMENTS 



It was found that these beetles could be killed with X-rays if 

 a sufficiently large dose were given, but it was noticed that the 

 beetles did not die for several days after they were rayed. Fur- 

 ther experiments indicated that the length of this latent interval 

 depended upon the amount of the X-ray dose, and there seemed 

 to be some evidence that this relation was approximately log- 

 arithmic. It was therefore decided to repeat these experiments 

 more carefully, first making sure that the effect was really due 

 to X-rays and not some attendant circumstance, and then in- 



2' A full bibliography of work done up to 1912 may be found in Fortschr. a.d. 

 Gebiete der Roent., 19, p. 123, 1912, in an article by Walter. A complete bibliog- 

 raphy of all X-ray work since 1912 has been published by Gocht. 



2- Chittenden, Bull. No. 4, New Series, Revised Ed. U. S. Dept. of Agr., p. 

 113, 1902. 



