MICROBIAL AIR INFLUENCE IN FERMENTATION, DISEASES, ETC. 19! 



may be of importance in a crowded work-room, but even under these con- 

 ditions it is probable that transmission of infection comes about more 

 frequently through actual contact or through food and drink. 



ORGANISMS or THE AIR AND FERMENTATIONS. A uniform inoculation 

 with soil bacteria such as produce the nodules on the roots of legumes is 

 obtained over considerable areas through the action of the wind in blowing 

 dust particles. The bacterial flora of milk is to some extent dependent 

 upon air currents as is also the development of the molds necessary to the 

 proper ripening of cheese, such as the Camembert. Acetic, butyric, and 

 other ferments are likewise distributed in this manner. The organisms 

 responsible for putrefaction and decay, the molding and spoiling of foods 

 are wind-borne. 



FREEING AIR FROM BACTERIA. Air is most commonly freed from 

 bacteria by sedimentation, for this is the ultimate fate of most dust par- 

 ticles. We have seen that they gradually subside in a quiet atmosphere. 

 When large quantities of pure air are required, dust and bacteria may be 

 removed by passage through a spray of water or through various types 

 of niters, such as cotton, glass, wool, etc. A familiar example of this type 

 of filtration is the laboratory use of cotton plugs in test-tubes. It is 

 sometimes necessary to resort to fumigation to destroy the organisms of 

 the air when an undesirable species is present. 



