66 BULLETIN 137, U. S. DEPARTMENT OF AGRICULTURE. 



and to interfere with the processes of cell division or multiplication, 

 causing, in some cases, degenerative changes to take place or a de- 

 crease in the rate of cell division. On the other hand, an exposure 

 o.f slight intensity or short duration may be without perceptible ef- 

 fect, or may even be accelerative, and perhaps increase the rate of 

 cell division. It seems to be well established that the effects of re- 

 peated exposures to the rays are to a certain extent cumulative, an 

 exposure of say 5 milliampere minutes having identically the same 

 effect, whether the exposure is given in one treatment or in several 

 treatments applied at different times so that the total exposure 

 amounts to 5 milliampere minutes. The effect of the rays on the sim- 

 pler forms of animal and plant life has been studied by numerous 

 investigators and in general their action seems to be the same as on 

 the higher animals. 



The X-ray process of treating tobacco has been exploited commer- 

 cially for sterilizing cigars infested with the tobacco beetle, and 

 satisfactory results have been reported. Improvements in the method 

 of treatment and in the apparatus have been made from time to 

 time, and the modern forms of Rontgen tubes used make possible 

 continuous and unchanging Rontgen-ray radiation of great power 

 and intensity. Effects can now be obtained which were not possible 

 or practicable in commercial work with the earlier forms of ap- 

 paratus. 



During 1912 experiments were made by Mr. A. C. Morgan and 

 the writer (76) with apparatus designed to sterilize cigars on a 

 commercial scale. The experiments, from a practical standpoint, 

 gave negative results. Later experiments made with apparatus 

 capable of producing and maintaining a much more powerful radia- 

 tion have shown that the earlier tests failed to give satisfactory re- 

 sults owing to the comparatively light exposures obtainable with the 

 apparatus then used. 



A brief statement of the results obtained by the writer (86) in a 

 series of experiments conducted under laboratory conditions at 

 Schenectady, N. Y., in 1915, is presented. 1 These experiments were 

 a continuation of investigations of a similar nature commenced at 

 Tampa, Fla. In previous experimental work it had been found in 

 sterilizing cigars or tobacco that light dosages are ineffective from a 

 practical standpoint. To be effective the radiation must be intense, 

 and it is evident that if the process can be applied successfully to 

 commercial work the apparatus used must be capable of producing 

 and maintaining such radiation during the entire period of exposure. 



The results obtained in the experiments have been briefly sum- 

 marized as follows : 



iA detailed report of these experiments has been published (86). 



