THE TOBACCO BEETLE. 65 



of fire or explosion if carbon clisulphid 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 

 greater when the air temperature is high. 



Formaldehyde as a Fumigant. 



Tests were made of 40 per cent formaldehyde at the rate of 2-| 

 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 embiyonic 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 Rontgen 

 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. 737 5 



