34 BACTERIA, YEASTS, AND MOLDS 



It is evident that drying may be conveniently used for 

 preserving cloth, leather, etc. Thorough airing and drying 

 by exposure to sunlight, followed by brushing, is the cure 

 for mildew. It is also well to remember that soiled clothes 

 mold much more readily than clean clothes, probably 

 because the dirt upon the cloth furnishes a little food for 

 the molds which suits them better than the cloth itself. 

 Soiled clothing, if packed away and left undisturbed for a 

 time, is quite likely to be injured by molding. 



While moisture is necessary for mold growth, it is true, 

 on the other hand, that too much moisture is generally 

 not favorable to molds. Very wet foods, like fresh meat, 

 milk, etc., do not commonly mold, although they readily 

 decay from the action of bacteria. 



Stagnation of the Air. Molds grow better in an atmos- 

 phere where the air is not freely moving, and therefore 

 are much more vigorous in foods shut up in tight boxes 

 than in the same foods when currents of air are allowed 

 to flow over them. The reason for this is not wholly 

 known. It may be that the agitation of the thread pro- 

 duced by the currents of air is injurious to the growth of 

 molds ; but it is more probable that the air currents simply 

 tend to evaporate the moisture from the surface too rapidly 

 to allow the growth of molds. Certain it is that a vigor- 

 ous growth of mold, upon a bit of cheese for example, 

 will, when exposed to the air, change from a fine, loose, 

 fluffy mass to a dense, flat, matted layer, and will soon 

 almost cease to grow. Whether this is due to evapora- 

 tion of moisture or to some other cause is a matter of no 

 great practical importance in the house. The/ac/ is borne 

 out by long experience, that molds grow in closed vessels 



