28 BACTERIA, YEASTS, AND MOLDS 



proper sustenance for mold growth. Leather, like that 

 of old shoes, if kept in a warm, moist atmosphere, becomes 

 covered with mildew. The same is true of carpets and of 

 woolen or cotton cloth. Such material does not furnish 

 a very luxuriant growth, the effect being commonly called 

 mildew instead of molding. At first sight there seems 

 little similarity between molding and mildew, but the 

 microscope tells us that mildew is really nothing more 

 than the growth of certain species of molds that have 

 not developed very luxuriantly. 



Paper is also liable to mold if kept damp, and certain 

 molds are occasionally found in and upon books. Even 

 woodwork will sometimes mold, especially in dark, damp 

 cellars. In short, almost anything in the household which 

 is of vegetable or animal nature may, under proper circum- 

 stances, furnish a substratum which can develop a more or 

 less luxuriant crop of these plants. 



RESULTS OF MOLD GROWTH 



The effect of mold growth varies with the species of 

 the mold and also with the material on which it is grow- 

 ing. Sometimes molds are useful, as for example in the 

 ripening of Roquefort cheeses. Upon most of our food 

 products, however, their action is injurious in at least 

 four directions, (i) They make the food unsightly, for 

 few people would be willing to use as food any material 

 upon which a luxuriant growth has made its appearance. 

 (2) They generally injure the taste of the foods, for a 

 peculiar flavor is sure to be imparted to any food product 

 where mold has grown, and after the mold has a luxuriant 

 growth the flavor of the food is so modified that we are 



