MECHANICAL VIBRATION 69 



formed (ozone, chlorine, acids, bases, ' etc.) , the same result 

 will follow (see Ozone, pp. 67, 138 and 145). 



RADIATIONS. 



Rontgen or x-rays and radium emanations when prop- 

 erly applied to bacteria will destroy them. The practical 

 use of these agents for the direct destruction of bacteria in 

 diseases of man of animals is restricted to those cases where 

 they may be applied directly to the diseased area, since they 

 are just as injurious to the animal cell as they are to the 

 bacteria, and even more so. Their skilful use as stimuli to 

 the body cells to enable them to resist and overcome bacteria 

 and other injurious organisms or cell growths is an entirely 

 different function and will not be considered here. 



PRESSURE. 



Hydrostatic pressure up to about 10,000 pounds per 

 square inch is without appreciable effect on bacteria as has 

 been shown by several experimenters and also by finding 

 living bacteria in the ooze dredged from the bottom of the 

 ocean at depths of several miles. 



Pressures from 10,000 to 100,000 pounds show variable 

 effects. Some bacteria are readily killed and others, even 

 non-spore formers, are only slightly affected. The time 

 factor is important in this connection. The presence of 

 acids, even CO2, or organic acids, results in the destruction 

 of most non-spore formers. 



MECHANICAL VIBRATION. 



Vibrations transmitted to bacteria in a liquid may be 

 injurious to them under certain circumstances. Some of 

 the larger forms like Bacillus suhtiUs may be completely 

 destroyed by shaking in a rapidly moving shaking machine 

 in a few hours. Bacteria in liquids placed on portions of 

 machinery where only a slight trembling is felt have been 

 found to be killed after several days. Reinke has shown 

 that the passing of strong sound waves through bacterial 

 growths markedly inhibits their developnient. 



