l64 BACTERIA, YEASTS, AND MOLDS 



the use of food procured from diseased animals. In the 

 process commonly adopted for drying milk, sufficient heat 

 is used to render harmless any disease germs it may have 

 originally possessed. 



A large variety oi fruits, berries, and vegetables are also 

 capable of preservation indefinitely by the simple process 

 of drying. The farmer's wife has long known that she 

 can preserve apples by cutting them into small pieces and 

 hanging them in strings over her kitchen fire to dry. The 

 same thing is possible for many vegetables, like squashes, 

 pumpkins, and even potatoes. Many kinds of berries — 

 blackberries, blueberries, strawberries, and some others 

 — can be preserved by merely extracting from them a 

 large part of their water. This drying of fruits and vege- 

 tables is often accomplished by subjecting them to artificial 

 heat, but more commonly in recent years the materials 

 are subjected to hydraulic pressure, by means of which 

 the water is actually squeezed out. A slight subsequent 

 drying is then sufficient to preserve the material almost 

 indefinitely. 



Some fruits are preserved by a combination of drying 

 and the presence of considerable sugar. Raisins, for 

 example, are dried grapes, but they are not dried so com- 

 pletely as berries, for some moisture is left in them. The 

 preservation of the raisin from decay is due in part to 

 the lack of water, but chiefly to the presence of a high 

 per cent of sugar, which is in itself deleterious to bac- 

 terial action. So, too, with other sweet fruits \^% prunes, 

 apricots, figs, dates, currants, etc. Their preservation is 

 partly a matter of drying and partly the result of the 

 sugar present. 



