X. ULTRASONIC VIBRATIONS 329 



struction of Arbacia eggs occurred in less than 1/1200 second. Their 

 photographs also showed that the eggs are first drawn out into spindle 

 or tadpole shapes and then are disintegrated. This suggested that 

 rapid fluid movement as the result of submicroscopic cavitation was 

 the main cause of disintegration. A time delay was noted in the 

 destructive action (-1/300 sec), which recently {22, S2) has been 

 found to be characteristic of cavitation. They also reported that 

 strong eddies first appeared in the cells of the plant Elodea with the 

 final result that the protoplasm or chloroplast became separated 

 from the cell wall and coagulated in the other places. Algae were 

 also torn to pieces. 



Red blood corpuscles in physiologic saline solution have also been 

 destroyed by ultrasonic radiation. Counts at the end of fifteen 

 second intervals showed that the percentage destroyed decreases as 

 time goes on until no more are affected unless the radiation intensity 

 is increased. Harvey (82) found that in all cases laking of blood was 

 associated with the expulsion of gas from a liquid in the form of 

 bubbles (cavitation) and that the type of gas did not matter unless 

 it was extremely soluble in water. That is, air, nitrogen, or hydrogen 

 all worked equally well but carbon dioxide did not. Furthermore, 

 gas bubbles formed before the sound exposure had no effect showing 

 that it was the bubble formation itself during exposure that accounted 

 for the destructive action. He found further peculiarities in the ef- 

 fect of the dissolved gas tension but these seemed to be associated 

 with the phenomenon of cavitation rather than with an intrinsic effect 

 on the organisms. For example, blood was laked under a gas pres- 

 sure of 100 lb. per square inch as long as the gas was not in equilibrium 

 with the liquid. However, if, at the same pressure, equilibrium were 

 established by thorough shaking of the liquid-gas mixture, a much 

 higher acoustic intensity was required. This supports the general 

 concept of cavitation phenomena as long as the gas-liquid equilib- 

 rium tension is considered rather than merely the applied pressure. 



In addition to kiUing many different types of small organisms, 

 larger animals such as fish, frogs, etc., have also been reported killed 

 or lamed in the sound field. This is to be expected since the sound 

 field would be present throughout their bodies and the ensuing de- 

 struction of some critical cell or group of cells would naturally produce 

 death or paralysis. As regards the death of larger animals, Harvey 

 (32) has found in the case of fish that the major cause is the destruc- 

 tion of the gill tissue and the blood corpuscles. 



