544 BIOLOGICAL EFFECTS OF RADIATION 



vibrations in the living cell, and only in part to the generation of heat 

 by convection currents. 



However, Christie and Loomis (5) pointed out that the method of 

 Schereschewsky for comparing the outputs of energy at different fre- 

 quencies was by no means correct, because the ammeter reading in the 

 resonating circuit, used as a standard by Schereschewsky, gives only an 

 indication of the peak of resonance in the secondary circuit, rather than 

 an absolute gauge of energy across the plates (see section on Apparatus). 

 Unfortunately, however, the method used by Christie and Loomis to 

 measure and compare the output across the plates was also incorrect. 

 They used the rate of heating of a saline thermometer placed between 

 the condenser plates as a gauge for comparison of the outputs developed 

 between the plates at different frequencies. McLennan and Burton (19) 

 pointed out that the saline thermometer could not be used in this sit- 

 uation because of the possibility that variation in frequency by itself 

 leads to an altered rate of heating for the same field intensity between 

 the condenser plates. 



McLennan and Burton proved that for several electrolytes, including 

 solutions of sodium chloride, there exists a specific concentration for 

 which at a constant wave-length a maximum rate of heating is developed. 

 These two workers and others have found that the maximum heating 

 will be shifted with the frequency independent of the field intensity 

 developed across the plates, and therefore the rate of heating in a saline 

 thermometer of a given concentration of sodium chloride cannot be used 

 to compare the output for different frequencies. 



Schereschewsky in his early work believed that he had demonstrated 

 a specific frequency band in which the mouse was killed much more 

 quickly than at other regions in this end of the spectrum, and that death 

 was not altogether due to internal heating. Christie and Loomis con- 

 cluded, albeit from procedures shown to be unsound, that there was no 

 specific action on the part of short electric waves and that the lethal effect 

 on mice was due solely to heat. 



These two more or less contradictory experiments leading to different 

 interpretations of the effect of the action of high-frequency electric fields 

 started a controversy which has continued to the present time. On the 

 one side are those workers who believe that the biological effects of this 

 radiation are due solely to the generation of internal heat — a heat gen- 

 erated perhaps by the setting up in the body of the exposed animal of 

 a displacement current. On the other side are those workers who believe 

 their experiments demonstrate an effect other than that of simple, inter- 

 nal heat. 



INTERNAL HEAT 



Attempts to measure the degree of heat generated in the living body 

 have given only approximate results, owing to mechanical and other 



