66 BULLETIN 737, 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 
of 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 hfe 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 R6éntgen tubes used make possible 
continuous and unchanging Réntgen-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 hght 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: | 
