24 BACTERIA, YEASTS, AND MOLDS 



fall upon it. These spores including species already 

 described, as well as a variety of others are almost sure 

 to be floating in the air, and one of the valuable practical 

 lessons for the housewife to learn is that the ordinary air 

 of her house is filled with mold spores which are sure to 

 get upon any food material that is left exposed. 



The mold spores, although very light, are slightly 

 heavier than the air, and after floating awhile they sink 

 to the floor, if the air is quiet, where they remain until 

 the air is again disturbed. Sweeping stirs them up, and 

 so does dusting. Fig. 18 represents two plates filled with 

 a jelly upon which molds will readily grow. . Plate I was 

 opened to the air for one minute in an ordinary room and 

 then closed. The room was then swept and Plate II was 

 exposed to the air for the same length of time. Both 

 were then set aside until the spores germinated, when the 

 photographs were made. The plate exposed to ordinary 

 air shows only one mold, while that exposed after the room 

 was swept contained large numbers. Dusting a room pro- 

 duces similar results. Even walking through a room, espe- 

 cially with long dresses that sweep the floor, will stir up 

 mold spores. The practical conclusions are thus taught 

 that wiping up dust with a damp cloth is far better than 

 dusting ; that carpet sweepers are better than brooms; and 

 lastly, that no food should be exposed to the air of a 

 recently swept room. 



PROTECTION OF FOOD FROM MOLDS 



The fact that the molding of food starts from spores 

 that drop upon it from the air suggests protecting the 

 food by the simple means of keeping the spores away from 



