110 DISINFECTION 



to disease in the guinea-pig, but did not interfere with its motility. Bruyuoghe 

 and Le Fevre de Arric (1925) stated that they were able to deprive the viruses 

 of rabies and of herpes of their virulence for rabbits by exposure in fairly high 

 dilution to radon, in a dose of 5 millicuries for 48 hours. Danysz (1906) 

 failed to produce any attenuation of the rabic virus by exposure for 20 hours 

 to the /S- and y-emanations from 20 mgm. of radium bromide, Bisceglie (1926) 

 claims to have lowered the virulence for guinea-pigs of a human strain of tubercle 

 bacillus by exposure of three successive generations to 5 mgm. of radium bromide, 

 the exposure being maintained for 5 days. Morphologically the bacilli of the 

 third generation had lost their acid-fast properties to a considerable degree ; thread 

 forms, occasionally showing branching, were numerous, and large numbers of 

 Gram-positive Much granules were visible. According to Suess (1908), exposure 

 of tubercle bacilli to highly active radium emanations for 2 days had apparently 

 no effect on their morphology, growth, or pathogenicity, von Schroetter (1927) 

 finds that bacilli and cocco-bacilli exposed to radon, in a dose varying for different 

 organisms from 0-5 to 40-0 millicuries of an intensity of 5-250 microcuries, tend to 

 elongate and become filamentous ; cocci, on the other hand, swell, increasing more 

 or less equally in size in all diameters. Spirochsetes do not change their size ; 

 they are eventually killed by the rays, but they remain motile for' a considerable 

 time. Spencer (1934, 1935) implanted radium needles in tubes of broth inoculated 

 with Salm. typhi, Proteus Z19, or Sir. pyogenes and incubated at 37° C. There 

 was at first a sUght retardation of growth, but after 24 hours the growth was 

 similar to that in control tubes. After 8-10 daily transfers the irradiated organisms 

 sometimes grew more luxuriantly and tended to develop filamentous forms or, 

 with streptococci, to grow in long chains. On the other hand irradiation at 

 0° C. proved fatal within a few days. Lea, Haines, and Coulson (1936) have 

 recently studied the effect of a and /5-rays on Bad. coli, Staph, aureus, and B. 

 mesentericus exposed in very thin gelatin films. Death of the organisms occurred 

 exponentially. The rate of disinfection was found to be independent of the tem- 

 perature, and proportional to the intensity of the radiation. All three organisms 

 were equally sensitive to a-rays, but towards ^-lajs B. mesentericus differed from 

 the other two organisms. The authors conclude that the action of the radiation 

 can be explained best on the " target " hypothesis. In a later paper Lea, Haines 

 and Coulson (1937) record that the death-rate of Bad. coli and B. mesentericus 

 exposed to y-radiation was of the exponential type, and that the mean lethal 

 ionization doses were approximately the same as those previously observed for 

 ^-rays. 



Sonic and Supersonic Waves. — Starting with the experiments of Wood and 

 Loomis in 1927, several observations have been made of recent years on the 

 destruction of organized cells by high-frequency sound waves (for references up 

 to 1932 see Chambers and Gaines 1932). Sonic waves, i.e. waves of audible 

 frequency, of about 8,900 cycles per second, produced by a nickel tube vibrating 

 in a strong electromagnetic field in resonance with a 2,000-volt oscillating power 

 circuit, are said to be able to bring about a considerable destruction of coliform 

 and certain other bacteria exposed to them for sufficient lengths of time. 



The method has been used by Chambers and Flosdorf (1936) for the liberation of 

 antigenic constituents from Salm. typhi and hsemolytic streptococci. Death was found to 

 occur logarithmically, the slope of the survival curve being a function of the sound intensity, 

 i.e. of the amplitude when the frequency was constant. The suspensions were not com- 



