ULTRASONICS — LAUFER 221 



The biological effects of ultrasonic waves are of particular interest. 

 In several cases the radiation has produced marked diminution in the 

 virulence of bacteria. Yeast cells lose their power of reproduction, 

 luminous bacteria lose their luminosity, and the mosaic virus of to- 

 bacco is powerfully deactivated. However, the growth of colon bacilli 

 cannot be influenced even by long exposure to high-intensity sound. 

 The bacteria in milk can be destroyed, permitting pasteurization at 

 low temperatures. Experiments undertaken by sugar refiners show 

 that the enzymes in sugar syrup can be destroyed to retard the inver- 

 sion of sucrose into glucose. Food decay has been halted for as much 

 as several weeks, indicating the possibility of sterilization of canned 

 foods through ultrasonics. The time required for the germination of 

 seeds has been changed, genes have been made to mature at abnormally 

 fast rates, and in some cases genes have been altered to yield unusual 

 mutations. 



At the Pennsylvania State College Acoustical Laboratory an ultra- 

 siren was used to kill roaches, mosquitoes, and mice. Laboratory 

 workers who were exposed to the sound reported unusual fatigue, 

 occasional loss of equilibrium even when wearing ear protectors, and 

 a disagreeable tickling sensation in the mouth and nose. At another 

 university, an attempt is being made to focus ultrasonic waves inside 

 living tissue in order to produce the destruction of cells in localized 

 regions. The treatment of deep-seated tumors with X-rays irradiates 

 not only the tumor but the intervening tissues as well. Focused ultra- 

 sonic radiation may possibly avoid the over-all destructiveness of 

 X-rays. Only further research can show whether this technique is 

 feasible. 



Whereas the field of ultrasonics is a logical extension of low-fre- 

 quency acoustics, the higher-frequency range provides a new tool 

 which can bring new aspects of nature into view. It is rare for a 

 physical phenomenon to have found within a few decades such wide 

 application in science and industry. In a broad survey such as the 

 foregoing, it is manifestly impossible to portray the great variety of 

 detail which has been developed in ultrasonic research, and only a 

 few of the interesting problems and applications have been mentioned. 

 Nonmilitary research in this field is still in its infancy, and many of 

 the observed effects have as yet no adequate explanation. Ultrasonics 

 today, a broad and beckoning field for research, holds forth the promise 

 of exciting new discoveries just beyond the horizon. 



