548 BIOLOGICAL EFFECTS OF RADIATION 



obtained definite attenuation of the three major toxins, diphtheria, 

 tetanus, and botuhnus. The effect was obtained without the develop- 

 ment in the toxin of temperatures that would by themselves affect the 

 potency of the toxin. 



Bennedetti (2), using diathermy, and later McKinley (13), using the 

 modern vacuum-tube circuit, obtained a slight acceleration of growth in 

 the early germination period of seedlings. In these experiments the 

 heat factor was presumably ruled out. 



Schliephake (33, 34) reported that staphylococci may be susceptible 

 to the direct action of ultra-high-frequency currents. They were not, 

 however, entirely convinced that the heat factor had been eliminated. 

 The organisms were exposed to the electric field in broth cultures. Szy- 

 manowski and Hicks (35) reported on a number of attempts to obtain 

 lethal action, or at least to stimulate dissociation, in pathogenic bacteria. 

 They treated the Dick hemolytic streptococcus of scarlet fever in broth 

 culture to a high-frequency field and in several experiments observed a 

 delay in growth. They did not observe any lethality or dissociation. 



Although the results of this work were essentially negative. Hicks and 

 Szymanowski expressed the opinion that it might be possible with a 

 smaller volume of broth, the use of a thin film of culture, and many 

 additional technical improvements with the short-wave generator to 

 demonstrate some action on bacteria. They also pointed out that the 

 selective absorption of broth cultures, wherein there may be large thermal 

 gradients between the broth, or continuous phase, and the organism, or 

 discontinuous phase, makes it difficult to determine the amount of 

 absorption in the bacterial cell itself. They thought that this factor 

 might be partially eliminated by working with a suspension in which 

 cellular elements constituted a high percentage of the total mass. 



Oartel and McKinley (24) found that treatment of the organisms 

 normally present in fragments of infected human teeth had a lethal 

 effect in 30.5 per cent of the samples treated. The arrangement or group- 

 ing of the organisms was affected in 15 per cent, the changes noted 

 being for the most part a change from streptococcus forms to diplococcus 

 forms, or from long chains to short chains. Also, of the total number 

 treated a marked reduction in size of the organisms was noted in about 

 15 per cent. Treatment was so adjusted in these experiments as to 

 avoid the generation of any measurable heat in the teeth fragments. 



Attempts to rule out the "heat factor" have usually been along two 

 lines : either by use of a constant temperature system or by treatment in 

 extremely weak fields. Szymanowski's experiment with toxins and 

 McKinley's work with germinating corn, both already described in this 

 paper, are cases in point. Both of these experiments, although they 

 strongly indicate specific effects other than heat, leave something to be 

 desired, since it is not absolutely certain that the small amount of heat 



