THE TOBACCO BEETLE. 65 
of fire or explosion if carbon disulphid were used. When pure, 
carbon tetrachlorid is a thin, oily fluid, and in the open air quickly 
evaporates. It is heavy (sp. gr. 1.599), transparent, colorless, and 
has a pungent odor—not, however, as disagreeable as in the case of 
carbon disulphid. | 
For fumigating it is used in the same manner as carbon disulphid, 
being evaporated from shallow pans placed over the substance 
treated. The evaporating area of the pans holding the liquid should 
be large. As with carbon disulphid, an exposure of from 24 to 48 
hours should be given. Tests made with carbon tetrachlorid in quan- 
tities up to 5 pounds per 100 cubic feet did not give satisfactory re- 
sults in sterilizing tobacco. As carbon tetrachlorid is more likely to 
be employed in small compartments it is well to use very heavy 
dosages, as the increase in cost will be slight. The killing effect is 
oreater when the air temperature is high. 
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/ 
FORMALDEHYDE AS A FUMIGANT. 
Tests were made of 40 per cent formaldehyde at the rate of 24 
ounces to 100 cubic feet of space. All stages of the tobacco beetle 
were used and the formaldehyde was vaporized by means of heat. The 
substance at this strength was found to be only partially effective. 
THE EFFECT OF RONTGEN OR X RAYS ON THE TOBACCO BEETLE. 
The effect of the X rays on the higher animals, including human 
beings, is well known. Sensitiveness to the rays has been found by 
different investigators to vary with the species of animal. Newly 
formed, especially embryonic tissues, have been found to be more 
easily affected by exposure to the rays than are those more mature. 
Certain bodies of cells are remarkably susceptible, their functions 
being retarded, modified, or completely inhibited, although mor- 
phologically they are apparently normal. The rays are known to 
have a marked effect on the reproductive organs, prolonged ex- 
posure causing an animal to become temporarily or permanently 
sterile. In general it may be said that when living tissues of an 
animal are exposed to the action of the rays, the functions of the 
cells are retarded or depressed, and permanent injury, or even the 
eventual death of the animal, may result. The exact effect of the 
rays depends upon the intensity of the radiation, the duration of 
the exposure, and the distance of the organism exposed from the 
source of radiation. When the energy input through a Roéntgen 
tube is great, the intense radiation resulting is correspondingly more 
active, and more injurious to living tissue, producing more marked 
physiological results. Exposure to rays of great intensity has been 
shown to retard or stop growth, differentiation and regeneration, 
75257 °—19—Bull. 787-—_5 
