XV 

 SHORT ELECTRIC WAVE RADIATION IN BIOLOGY 



G. Murray McKinley 



Zoological Laboratories, University of Pittsburgh 



Introduction. Biological effects. Internal heat. Synthetic fever. An effect other 

 than heat. Conclusions. Apparatus: General description — Push-pull oscillator — Half- 

 wave oscillator. References. 



INTRODUCTION 



We are already familiar with the far-reaching effects obtained in 

 biology by the use of gamma rays, of X-radiation, of ultra-violet, of light, 

 and of infra-red. We know that all of these form one great, continuous 

 spectrum of electromagnetic waves, the various regions of which differ 

 only in wave-length. Beyond the near infra-red is the radiation used 

 by radio, which extends this spectrum into regions of very long waves, 

 now commonly called Hertzian or electric waves. 



Although this spectral band is continuous, there are still gaps not 

 yet adequately filled by instrumental means, as, for example, the gap 

 between X-rays and ultra-violet. Another great gap, now being rapidly 

 filled, lies between the near infra-red and the weaves of wireless. It is 

 only recently that short-wave radio transmission became a fact and 

 advance in this direction has led to a continued reduction in the 

 length of waves obtainable. This has largely been made possible by 

 improvement of the three-electrode vacuum tube. 



The modern short-wave vacuum-tube oscillator has permitted the 

 study of the action of electric waves of a meter or less, and with such 

 technical progress, research in the biological effects of this type of radi- 

 ation has become increasingly important. The invention of the three- 

 electrode vacuum tube has been the door which opened to the biologist 

 a whole new world of radiation. The region is inconceivably vast, 

 extending from the near infra-red to a theoretical infinity, and it might 

 seem quite difficult for the biologist to decide upon some locality as most 

 suitable and promising for experimentation, were it not for certain 

 practical and mechanical restrictions. The present-day vacuum tube, 

 although one of the most marvelous of our physical instruments, is still 

 unable to generate in adequate intensity wave-lengths of much less 

 than 1 meter, so that the region of shortest electric waves cannot at pres- 

 ent be utilized in biology. Again, apparatus generating wave-lengths 

 much longer than 100 meters is not convenient in biology, and the 



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